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Fretp CotumBiaNn MusEvuM. 


PUBLICATION 73. 


GEOLOGICAL SERIES. Vor lis No: |. 


NORTH AMERICAN 
PLESIOSAURS. 


PAARL TS. 


BY 


SamueL W. Wuutston, M.D., Pu.D., 


Associate Curator, Division of Palzontology ; 
Professor of Paleontology, University of Chicago. 


‘ie Ouiver C. Farrincton, Pu. D., 
Curator of Geology. 
' 
8 Cuicaco,4U 5.2A: 


April, 1903. 


Fretp CoLuMBIAN MuSEuM. 


PUBLICATION 73. 


GEOLOGICAL SERIES. Voz. II, No. 


NORTH AMERICAN 
RE ESorOSAU RS: 


f ghe iP age SRT 


BY 


SAMUEL W. Wittiston, M.D., Pu. D., 


Associate Curator, Division of Palzontology ; 
Professor of Palzontology, University of Chicago. 


Oxiver C. Farrinctron, Pu. D., 


Curator of Geology. 


Cnuicaco, .U. S. A. 
April, 1903. 


Se. 


a 


- 


NORTH AMERICAN PLESIOSAURS. 


PART FT. 


BY SAMUEL W. WILLISTON, 


CONTENTS. - 

: . PAGE 
Introduction, ; : : , ; ; ; : : ; ; , 3 
Bibliography and catalogue of North American Plesiosaurs, . ; : 7 
Dolichorhynchops osborni Williston. Description of skeleton, with restor- 

ation, ; ; ‘ ; he) : , ; ; 13 
Cimoliasaurus snowii Williston. Description of skull and neck, aes 2 
Brachauchenius lucasii Williston. Description of skull, vertebree and ribs, 57 
Polycotylus latipinnis Cope. Description of paddle, ip ; OSs 
Polycotylus ischiadicus Williston. Description of pelvis, . ; : 2 
Plesiosaurus gouldii Williston. Description of dorsal vertebra, : eal 2 
Propodial bones of young Plesiosaurs from the Cretaceous of Kansas, . 73 
A peculiar food-habit of the Plesiosaurs, . ; j ; : 7 raters 


Plates I to XXIX, : i , ; : 3 ‘ "Ate 


INTRODUCTION. 


There are few orders of reptiles, so long and so widely known as 
are the plesiosaurs, of which our knowledge is more unsatisfactory. 
It has been within the past decade only that a tolerably complete 
knowledge of any form has been obtained, thanks largely to the 
researches of Seeley, Dames and Andrews. Especially is our ignor- 
ance of the American forms yet great. Very few figures or adequate 
descriptions have been published of our numerous and diverse types. 
Not only are the specific characters of the descriptions almost wholly 
undecipherable, but the generic characters even can be satisfactorily 
made out in but few. Thirty-two species and fifteen genera have 
been described from the United States, and in not a single one of 
them has there been even a considerable part of the skeleton made 
known. The skull is known in but three species, and in only one has 
there been any description of it. With the exception of a sketch of 
the incomplete girdles of E/asmosaurus platyurus, and of a few limb 
bones by Leidy, with an outline figure of a Mega/neusaurus paddle by 
Knight, nothing of the extremities has been published. And yet, 
specimens of plesiosaurs are not at all rare in American deposits and 
collections. 

Although most of the genera and species of the United States 
have been founded on such scant material, and even more scanty 
descriptions, that their identification is almost impossible, except by 
actual comparison of the type specimens, it is not at all improbable 
that nearly all the names which have been proposed will eventually 
be found valid. The group has a wide geological range, from the 
Jurassic to the uppermost Cretaceous, nearly every epoch being repre- 
' sented by one or more species. 

The writer has for some time given such attention as his duties 
permitted to the study of the American plesiosaurs, in the hopes 
eventually of clearing up much of the confusion now existing con- 
cerning these animals, and the present paper was intended to be pub- 
lished as a portion of this monographic study. As, however, the 
publication of so extensive a paper must be deferred for some time, 
he has thought best to publish that portion now prepared in advance 

3 


4 Fretp CoLumpian MustumM—GEeEo toecy, VoL. II. 


of a more final review of the subject. The present paper contains 
detailed descriptions of Dolichorhynchops osborni Williston and Brach- 
auchenius lucasi Williston; a revised description of Cimoliasaurus 
snowit Williston, together with certain descriptions of and remarks 


upon such other forms from the Kansas Cretaceous as bear more 


or less directly upon the principal species here discussed. As 
will be seen from the list given below, no less than nine distinct 
species of plesiosaurs have been described from the Kansas Cretaceous, 
all of which, except one or two, are autoptically more or less known 
to the writer, together with nearly as many more hitherto undescribed. 


The true generic determination of the most of these species is impos- . 


sible at present. So little is known of the real generic characters, not 


only of the American but also of the. European plesiosaurs, that, — 


unless specimens are very complete, it is impossible to correctly 
assign them. Furthermore, there is in many respects such wide 
diversity between the different forms now known that almost every 
species seems rightfully to belong in a different genus. On the other 


hand, in our present ignorance of their value, generic differences can, 


rarely be recognized unless one has a considerable portion of the skel- 
eton. Generic determination is, therefore, for the most part, at the 
present time simply guess-work. In the present paper I have, for 
convenience sake, given names to some of these new forms, but the 
generic names are always provisional, and the specific names also 
insome cases. Cvmoliasaurus snowiti | do not believe is congeneric with 
the type species of the genus; it belongs as well in several other 
genera proposed by American writers. I do not see, however, much 
use in giving new generic names to every form until some razson @ étre 
can be discovered for them. I have departed from this conviction in 
proposing two new generic names for species herewith described, 
largely because the specimens upon which the names are based are 
more than usually complete, and because there seems to be positive 
characters to sustain the names. 

The full description and illustration of Dolichorhynchops osborni 
will, I trust, aid in the solution of many of these generic problems; 
they will at least furnish a means of comparison for other forms known 
already or to be discovered in the future. 

A second part of this work is to follow soon, I trust. It will 
contain the descriptions and illustrations of two or three other skulls, 
different in structure from those herewith described and from each 
other, together with other important material. 

Iam glad to express my thanks to Prof. Dr. E. Fraas for kind 


Apr. 1903. NorrH AMERICAN PLESIOSAURS—WILLISTON, 5 


suggestions, and for the communication of photographs; and to Prof. 
H. F. Osborn for kind favors. 


Seeley* has proposed to divide the plesiosaurs into two chief 
groups, the Dicranopleura, including those forms with double-headed 
ribs in the cervical region, both long-necked (Dolichodeira) and short- 
necked (Brachydeira); and of which singularly no certain representa- 
tives have been discovered in America; and the Cercidopleura, those 
with single-headed ribs, also including both long-necked and short- 
necked types. Cope in 1887+ proposed the two sub-families: Pody- 
cotyline for those with broad epipodial bones; and the /P/estosaurine 
for those with elongated epipodial bones, of which there are no 
certain representatives in America. But objections may be urged 
against both of these classifications. Certain. forms very closely 
allied to P/osaurus,a dicranopleuran, have single-headed ribs through- 
out. Polycotylus is a short-necked type, with single-headed cervical 
ribs, and it seems almost certain that certain long-necked forms that 
should be widely separated have also broad epipodial bones. 

Nevertheless, I feel pretty confident that the final classification of 
the Plesiosauria will include three or four distinct families and twenty 
or thirty well-defined genera. There is scarcely a group of extinct 
reptiles, unless it be the Dinosauria, which offers more divergent 
characters than do the plesiosaurs. The skull may be long and 
slender or short and broad; the teeth.irregular in size and large, or 
small and nearly uniform; the prefrontals and postorbitals separated 
or suturally united; the parietals with a high thin crest, dr without 
such a crest; the palatines widely separated or broadly contiguous; 
the supraoccipitals paired or single(?). The neck may include as few 
as thirteen vertebrae or as many as seventy-two, the vertebre all 
_very short or the posterior ones elongated; the ribs single or double- 

headed; the arches anchylosed to the centra or suturally free through- 
out life: The dorsal vertebra may be no longer than the anterior cervi- 
cals or much elongated; all the vertebra may have conspicuous 
vascular foramina below or be without them; the diapophyses may 
be much elongated and situated low down, or shorter and situated 
high, up; the vertebral spines elongated or short. In the pectoral 
girdle there may be a long epicoracoidal process; the clavicles and 
episternum either present or absent. The epipodial bones are two 


* Proc. Royal Soc. Lond. 1892, 151. 
t+ American Naturalist, 1837, 564. 


6 Fietp Cotumpian MuseuM—GEOo.ocGy, VoL, II. 


in number and elongated, or three or four and broad. The ilium may 
differ in its mode of attachment and the form of both pubis andischium 
may differ much. 

Certainly among all these characters, and probably not a few 
others, there will be no dearth of material for classification. Unfor- 
tunately there are yet many forms in which we do not know what 
relations these different characters bear to each other, and until we 
do, any classification must be provisional. I believe that most 
herpetological taxonomists will agree with me that the differences 
between Dolichorhynchops and Brachauchenius are more than generic in . 
value, and I doubt not that differences of equal value will be discov- 
ered in yet other species when we shall know more about them than 
we do at present. 

The origin of the Plesiosauria I will discuss in a later paper. 
For the present, I may say that I believe that their nearest affinities 
among all reptiles, recent or extinct, are with the Dicynodonts. 


CATALOGUE AND BIBLIOGRAPHY OF THE NORTH AMERICAN 
PLESIOSAURIA. 


PLESIOSAURUS. 

Conybeare, Trans. Geol. Soc. Lond. v, 560, 1821. 

BREVIFEMUR Cope, Cret. Vertebr. 256, 1875.—Greensand No. 5, New 
Jersey. 

Cimoliasaurus magnus (Leidy) Cope, Ext. Batrach. 1869, 43, 

ff. 13-15. 

*GuLo Cope, Proc. Acad. Nat. Sci. Phil. 1872, 228; Cret. Vert. 1875, 
256.—Fort Pierre Cretaceous, Kansas (evrere, Niobrara). 


*mupGeEI Cragin, Fifth Pub. Colorado Col. Sci. Soc. 69, ff. 1-3.— 
Comanche Cretaceous, Kansas. 


*couLtpu Williston, Kansas Univ. Quart. vi, 57, 1897.—Comanche 
Cretaceous, Kansas. 


SHIRLEYENSIS Knight, Amer. Journ. Sci. 1900, p. 115.—Jurassic, 
’ Wyoming. 
All of the foregoing species were based upon fragmentary mate- 
rial, and it is improbable that any belong in the genus P/eszosaurus. 


CIMOLIASAURUS. | 
Leidy, Proc. Acad. Nat..Sci. Phil. 1851, 325 (1852). 


MAGNUS Leidy, l. c.; ibid. 1854, 72, pl. ii, ff. 4-6; Cretac. Rept. 1865, 
25, pl. v, ff. 13-19, pl. vi; Cope, Ext. Batrachia, etc. 186y, 
42; Lydekker, Cat. Fos. Rept. Brit. Mus. 11, 211.—Creta- 
ceous No. 5, New Jersey. 


PLANIOR Leidy, Proc. Acad. Nat. Sci. Phil. 1870, 22.—Cretaceous, 
New Jersey (see also Discosaurus). 


*snowil Williston, Science, xvi, 262; Trans. Kansas Acad. Sci. xii, 
174, 1890; Cope, Proc. Amer. Phil. Soc. xxxiii, 109.— Nio- 
brara Cretaceous, Kansas. 

LARAMIENSIS Knight, Amer. Jour. Sci. x, 117, 119.—Jurassic, Wyo- 
ming. 

ie 


8 Fietp Co_umpian MusrtuM—GEo vocy, Vot. II. 


This genus was based*‘upon vertebral centra alone, from the 
cervical, dorsal and caudal regions; the author, however, referred 
them all erroneously to the dorsal and lumbar regions. The type is 
well figured in Leidy’s work on Cretaceous Reptiles, plates v and vi. 
The vertebre have infracentral vascular foramina. The ribs are 
single-headed. The largest centrum measures 110 millimeters in 
the greatest diameter. This genus has served as a sort of waste 
basket for the reception of fragments and poorly known forms. C, 
snow is known froma skull and long neck. It can scarcely belong 
in C’moliasaurus. 


DISCOSAURUS. 
Leidy, Proc. Acad. Nat. Sci. Phil. 1851, 326 (1852). 


PLANIOR Leidy, Proc. Acad. Nat. Sci. Phil. 1870, 20; 22; Cope, Cretac. . 


Vert. 1875, 255 (Cimoliasaurus).—Cretaceous, Mississippi. 
Discosaurus vetustus Leidy, Cretac. Reptilia, 23, pl. 5, ff. ro—r2. 


verustus Leidy, ‘Cretac. Reptilia, 22, pl. iv, ff. 13-18, pl. v, ff. 1-9; 
Proc. Acad. Nat. Sci. Phil. 1851, 326; Cope, Ext. Batrachia. 
etc. 256; Amer. Journ. Sci. 1870, 141;  Cretac. Vert. 1875, 
255 (Cimoliasaurus).—Cretaceous, Alabama. 


This-genus was based upon the mutilated bodies of two caudal 
vertebre from the Cretaceous of Alabama. Leidy associated with 
these other mutilated vertebre from the Cretaceous of Mississippi, 
New Jersey and Alabama. Cope suppressed the name, as of a genus 
insufficiently differentiated from Czmoliasaurus. This is quite true, as 
it is also true of several of Cope’s own genera of the plesiosaurs, It 
is not at all improbable, however, that there are different species, and 
perhaps different genera represented by the specimens Leidy described 
and figured. oS 


BRIMOSAURUS. 
Leidy, Proc. Acad. Nat. Sci. Phil. 1854, 73. 


GRANDIS Leidy, Proc. Acad. Nat. Sci. Phil. 1854, 73, pl. i, ff. 1-3; 
ibid. 1870, 10; ibid. 1871, 22 (Déscosaurus); Cope, Ext. 
Batrachia, etc. 1869, 43,54 (Cimoliasaurus); Proc. Bost. Soc. 
Nat. Hist. 1869, 266 (¢d¢.); Amer. Journ. Sci. 1870, 269 (¢@.), 
Rep. Geol. Surv. Terr. 1871, 400 (¢¢.); Cretac. Vert. 1875, 
255 (#d¢.)—Cretaceous, Arkansas. 


This genus and species were founded upon more or less imperfect 


a 


Apr. 1903. NortH AMERICAN PLESIOSAURS—WILLISTON. 9 


dorsal vertebre from the Cretaceous,’ probably Benton, of Clark 
County, Arkansas. Cope suppressed the generic name as of a genus 
‘not sufficiently differentiated from Cimoliasaurus. I believe, however, 
that both genus and species are valid; and that the former will include 
some of the species from Kansas. Lambe has identified the species 
from the Belly River Cretaceous of Canada, but it seems to me that 
the identity must be more or less problematical. 


| ELASMOSAURUS. 
Cope, Proc. Acad. Nat. Sci. Phil. 1868, 68. 


*pLATYURUS Cope, l. c.; Notes on Geology, Leconte, 1868, 68; Proc. 
Bost. Soc. Nat. Hist. 1869, 266; Amer. Nat. ii, 87; Ext. 
Batrachia, etc. 1869, 47, ff. 7-12, pl. 11, ff. 1-9, pl. iii; Amer. 
Jour. Sci. 1870, 140, 268; Amer. Nat. v, 47; Rep. U. S. Geol. 
Surv. Terr. 1871, 393, 1872, 320, 336; Cretac. Vert. 1875, 44, 
79, 256; Bull. U. S. Geol. Surv. Terr. ili, 1877, 578; Amer. 
Nat. xxii, 724; Leidy, Amer. Jour. Sci. xlix, 1870, 392; Proc. 
Acad. Nat. Sci. Phil. 1870, 9, 18; Lydekker, Cat. Foss. Rept. 
Brit. Museum, ii, 181 ( Cimol/iasaurus).—Fort Pierre Cretace- 
ous, Kansas. 


INTERMEDIUS Cope, Proc. Amer. Phil. Soc. 1894, 112.—-Fort Pierre 
Cretaceous, South Dakota. 


ORIENTALIS Cope, Proc. Acad. Nat. Sci. Phil. 1868, 313; Proc. Bost. . 
Soc. Nat. Hist 1869, 266; Geological Surv. New Jersey, 
Cook, Append. (1868), 1869, 733; Amer. Nat. 1869, 87; Ext. 
Batrachia, etc. 1869, 44, 55, pl. ii, f. 10; Amer. Jour. Sci. 
1870, 368; Cretac. Vert. 1875, 255; Bull. U. S. Geol. Surv. 
Terr. ili, 1877, 567, 578; Am. Nat. xi, 1877, 311; Leidy, Proc. 
Acad. Nat. Sci. Phil. 1870, 22 (Déscosaurus).—Greensand No. 
4, New Jersey. 


SERPENTINUS Cope, Bull. U. S. Geol. Surv. Terr. iii, 578, 1877; Amer. 
Nat. xi, 1877, 311.—Niobrara Cretaceous, Nebraska. 


The genus Z/asmosaurus was founded upon a nearly complete 


_ series of vertebra obtained near the vicinity of Fort Wallace, Kansas, 


wrongly ascribed to the Niobrara epoch. The neck was very long. 
The incomplete girdles are also known. No additional material has 
been ascribed to the type species since the original description by 
‘Cope. . 


ae) Fretp CoLumMbiAN MusrEuM—GEOLoGy, VoL, II. 


POLYCOTYLUS. 
Cope, Proc. Amer. Phil. Soc. xi, 117, 1869. 
*LATIPINNIS Cope, |. c.; Ext. Batrachia, etc. 36, pl. 1, ff. 1-12; An. 
Rep. U. S. Geol. Surv. 1871, 388; ibid. 1872, 320, 335; Bull. 
U. S. Geol. Surv. Terr, 27, 1874; Cretac. Vertebrata, 45, 72, 
255, 1, vil, ff. 7, 7a; Leidy, Ext. Vert. Fauna, 279.— Niobrara 
Cretaceous of Kansas. ; 


*IscHIADICUS Williston, postea, Niobrara Cretaceous, Kansas. 


This genus was based upon a portion of a propodial bone and 
imperfect cervical and dorsal vertebre. The ribs of the neck are 
single-headed. 


- PIRATOSAURUS. 
Leidy, Cretaceous Rept. N. Amer. p. 29, 1865. 


pLicatus Leidy, |. c. pl. xix, fig. 8.—Cretaceous, Minnesota. 


Based upon a single tooth. Believed by the author to be Cro- 
codilian. The horizon is probably Niobrara, judging from the 
accompanying fossils. If so, it would seem very probable that the 
tooth belongs to a plesiosaur, though rather sharply conical in shape. 


NOTHOSAUROPS. 
Leidy, Proc. Acad. Nat. Sci. Phil. 1870, 74. 
occipuus Leidy, |. c.; Rep. Geol. Surv. Terr. 1873, i, 345, pl. xv, ff. 
11-23; Cope, Bull. U.S. Geol. Surv. Terr. i, 28, 1874 (P/esio- 


saurus);Cretac. Vert. 1875, 256 (¢d.).—Laramie [| ?] Cretaceous, 
Dakota. 


TAPHROSAURUS. 
Cope, Proc. Amer. Phil. Soc. xi, 274, 1870. 


: { 
LOcKwoop1 Cope, Ext. Batrachia, etc. 1869, 40 (Plestosaurus); Proc. 
Amier. Phil. Soc. xi, 274.—Cretaceous No. 1, New Jersey. 


OLIGOSIMUS. 
Leidy, Proc. Acad. Nat. Sci. Phil. 1872, 39 (1873). 


GRAND&VUS Leidy, 1. c. 40; Extinct Vert. Fauna, 286, 345, pl. xvi, 
ff. 18, 19.— 


This genus and species were proposed for a detached caudal 
vertebra of small size, without definite horizon, from Green River, 


Apr. 1903. NortrH AMERICAN PLESIOSAURS—WILLISTON. II 


Wyoming. The processes are attached. The description will apply 
to caudal vertebre of various genera. 


URONAUTES. 
Cope, Proc. Acad. Nat. Sci. Phil. 1876, 345. 


CETIFORMIS Cope, Il. c. 346.—Fort Pierre (?) Cretaceous, Montana. 


specIES Cope, Amer. Nat. 1887, 566.—Fox Hills Cretaceous, New 
Mexico. 


This genus was based upon cervical, dorsal and caudal vertebre. 
The cervicals are short, with the prereenes partly attached, and the 
ribs single-headed. 

Professor Cope referred the type species to the Fox Hills Cre- 
taceous with doubt. I suspect, rather, that the horizon is Fort 
Pierre. 


OROPHOSAURUS. 
Cope, Amer. Naturalist, 1887, 564. 
pauctporus Cope, |. c.—Fox Hills Cretaceous of New Mexico. 


Based upon parts of three cervical vertebrae. The neural arches 
are codéssified, the ribs free. Centra short; ribs single-headed. 


PIPTOMERUS. 
Cope, Amer. Nat. 1867, 564. 
MEGALOPORUS Cope, l. c. 564.--Fox Hills Cretaceous, New Mexico. 
MiCROPORUS Cope, |. c.—Fox Hills Cretaceous, New Mexico. 
HEXAGONUS Cope, |. c.—Fox Hills Cretaceous, New Mexico. 


This genus and species are based upon cervical and dorsal verte- 
bre only. The cervicals are short, the processes free and the ribs 
single-headed. 


TRINACROMERUM. 
. Cragin, Amer. Geologist, Dec. 1888. 


*RENTONIANUM Cragin, |. c.; ibid, 1891, 171.—Benton Cretaceous, 
Kansas. 


A large part of the skeleton was known to the describer, includ-> 
ing the skull, vertebra, part of the girdles and limbs. 


12 FieLp CoLuMBIAN MusgEuM—GEOLOoGY, VoL. II. 


PANTOSAURUS. 


Marsh, Report Geological Congress, 1891, 159; Amer. Journ. Sci. 
xli, 1895, 406; Parasaurus Marsh, Amer. Journ. Sci. xliii, 
338, 1891 (preoccupied). 


srriAtus Marsh, Amer. Journ, Sci. xliii, 338, 1891 (Parasaurus); ibid, 
i, 406, 1895, ff.—Baptanodon Beds, Wyoming. 


Based upon a posterior cervical centrum. | ‘‘ Vertebre strongly 
erqoved. Neck long and slender, the vertebre preserved resemble 
most in form and size those of Plestosaurus plicatus Phillips.” 


EMBAPHIAS. 
Cope, Proc. Amer. Phil. Soc. 1894, 111. 
CIRCULOSUS Cope, l. c.—Pierre Cretaceous, South Dakota. 


This genus and species were founded on three vertebra, cervical 
and dorsal.» The cervicals are short, with persistent sutures. Ribs 
double-headed(?). 


MEGALNEUSAURUS. 
Knight, Amer. Journ. Sci. v, 1898, 375. 


REX Knight, Science, 1895, 449 (Cimoliasaurus); Amer. Journ. Sci. v, 
1898, 379, ff. 1-3.—Jurassic, Wyoming. 


A large portion of the skeleton of the type species is known; the 
parts so far described are the vertebra and limbs. 


* DOLICHORHYNCHOPS. 
Williston, Kansas Univ. Sci. Bulletin, No. 9, p. 141, Sept. 1902, 


*osporn1 Williston, l. c.—Niobrara Cretaceous, Kansas. 


BRACHAUCHENIUS. 
Williston, postea. 


*:_ucast Williston, postea.—Benton Cretaceous, Kansas. 


~ Apr.1go3. Nortu AMERICAN PLESIOSAURS—WILLISTON. 13 


DOLICHORHYNCHOPS OSBORNI. 


‘The specimen of Dolichorhynchops osborni herewith described and 
illustrated was discovered by Mr. George Sternberg in the chalk of 
Logan County, Kansas, in the summer of 1900, and skilfully collected 
by his father, Mr. Chas. H. Sternberg, the veteran collector of fossil 
vertebrates. The specimen was purchased of Mr. Sternberg in the 
following spring for the University of Kansas, where it has been 
mounted and where it now is. When received at the museum the 
skeleton was almost wholly contained in a large slab of soft yellow 
chalk, with all its bones disassociated and more or less entangled 
together. The left ischium, lying by thé side of the maxilla, was. 
protruding from the surface, anda part of it was lost. The bones of 
the tail and some of the smaller podial bones were removed a little 
distance from the rest of the skeleton, and were collected separately 
by Mr. Sternberg. The head was lying partly upon its left side and 
some of the bones of the right side had been macerated away; the 
maxilla indeed had disappeared. 

The task of removing and mounting the bones has required the 
labor of Mr. H. T. Martin the larger part of a year, and is, as finally 
mounted, an example of great labor and skill on his part. For the 
position of the bones in the recreated skeleton and their general 
arrangement I am of course responsible. There is some little doubt 
as to the exact position of the pectoral girdle, as respects the ribs and 
vertebrae. The position as shown in the restoration is that which 
seemed, upon the whole, most nearly the truth, judging from the 
_ figured skeletons of P/esiosaurus. There is also some doubt about 
the proper length of the tail. The relations of the preserved centra 
seemed to indicate a loss of a few vertebre in this region, and for 
that reason four plaster models have been intercalated. There are 
nineteen vertebre preserved in the neck; there may have been one 
more, or possibly two, but for reasons discussed further on this is 
doubtful. In the dorsal region there are thirty vertebrae, three of 
which may be called pectoral. Twenty-five are preserved in the tail. 
The skull, after its complete removal from the matrix, was found 
to be so very fragile that it was not thought expedient to mount it. 
It was also somewhat distorted, as will be seen from the illustrations. 
A model, therefore, was made under my careful supervision, and 
mounted in its stead. The skeleton as mounted is just ten feet in 


14 Firetp Cotumpian MustEumM—GeEotocy, Vo. II. 


length. The neck in life must have been thick and heavy at the base, 
tapering rapidly from the trunk to the head. The'trunk was broad, 
as is evident from the position of the ribs, with the under side not flat, 
as might be supposed, but strongly convex from side to side. The 
abdominal region proper, between the girdles, must have been short, 
and could not have been very distensible. The short tail was thick atits 
base, as is conclusively shown by the attachment of the ilia and the 


elongated ischia. Furthermore, the fore legs, at least, must have. 
been enclosed for a considerable distance at their attachment by the ~ 


skin and muscles of the pectoral region; they could not have been 
pedunculated to the extent that they are usually represented to be in 
the restorations. The species was named in honor of Prof. H. F. 
Osborn of Columbia University. 

The distinguishing characters, both family and generic, may be 
summed up as follows: 


Do.icHorHyYNcHops.— Head elongate, the facialregion much attenuated; 
teeth nearly untform in size, small; prefrontal and postfrontal bones not 
joined; partetals extending into a high crest; supraoccipital bones separated; 
tnternal nares small, included between the vomer and patatine only; pala- 
tines broadly separated throughout; a large vacuity between the pterygoids 
anteriorly; quadrate process of pterygoids short. Neck but little longer 
than the head, composed of nineteen or twenty vertebre; all presacral 
vertebre of nearly equal length, moderately concave, and with vascular 
foramina below; spines short, uniform in length; diapophyses of the dorsal 
vertebre situated high up. Coracotds with long epicoracoid process; 
clavicles and scapule free; episternum with an emargination tn front and 
behind, the latter forming part of a large interclavicular foramen. 
Three epipodial bones, all broader than long. Tschium elongated. 
Length ten feet. 


Sxutt.—The skull of Dolichorhynchops osborni is of a remarkably 
elongate and slender form, attenuated in front.of the orbits, and with a 
thin, high, parietal crest. The region between the eyes is very nar- 
row, the superior temporal vacuities large, and the teeth numerous 
and slender. The head is more nearly of the typical aquatic fish-eat- 
ing type than is perhaps known in any other plesiosaur, and the neck 
is as short as or shorter than in any other ‘plesiosaur hitherto 
described. The skull, as received, was lying partly upon its left side, 
with a part of the right side separated and injured, some of the bones 
having been macerated away. The specimen was completely removed 
from the matrix, including even that which was between the bones, 
and the elements of the brain case were separated out. In conse- 


Apr. 1903. NorrH AMERICAN PLESIOSAURS—WILLISTON. 15 


‘ 


quence, the fragility of the skull was such that it was not deemed 
prudent to mount it with the remainder of the skeleton. A model of 
it was therefore made, based upon my drawings and studies, and 
which, I think, represents the skull very nearly as it must have been 
during life. Its width in all parts may not have been accurately 
determined, but the discrepancies from the reality can not be great. 

‘The premaxillaries are separated from each other distinctly by 
suture, the long facial processes apparently lying in contact with each 
other without close union. The suture separating them from the 
maxilla begins just back of the sixth tooth; it curves upward and 
backward for a short distance, and then runs parallel with the upper 
border as far back as the narial opening, whence the margin runs more 
obliquely to the tip of the processes above the middle of the orbit. 
Each premaxilla bears six teeth, which are among the largest of the 
jaws, and are all of nearly uniform size, the first one curved forward. 
The facial process is slender, flattened on its opposing, sutural sur- 
face, and with its external, convex surface distinctly striated longi- 
tudinally. The dentigerous portion is convex, pitted toward the 
anterior part, and about twenty- five millimeters in height, opposite 
the last tooth. The relations of the bone on the palatal surface can 
not be determined. 

The maxi//e are long and narrow on the facial surface, and 
very narrow on the palatal surface, at least posteriorly. They bear 
twenty teeth on each side, the first ten or eleven of which are 
of nearly equal size, and scarcely smaller than those of the pre- 
‘maxilla. The posterior ten teeth are crowded, occupying a 
space less than one-half that of the preceding ten, and they are 
smaller. The greatest width of the maxilla on the facial surface 
—about twenty-five millimeters—is at about seventy millimeters in 
- front of the orbit, whence the bone narrows to a width of ten milli- 
meters below the anterior border of the orbit. Below the orbit, the 
bone extends as a narrow bar, becoming slightly narrower posteriorly, 
before the beginning of the jugal suture. Beyond this, it flattens 
posteriorly to near its extremity, which is about midway of the tem- 
poral bar, and one hundred millimeters beyond the last tooth. 

There are twenty-five or twenty-six teeth in each jaw. They are 
inserted by a long fang, the pulp cavity of which occupies more than 
one-third of the diameter, extending a short distance into the crown. 
In the largest teeth, the crown is about twenty millimeters in length, 
with a diameter at the base of six millimeters. The crown is rela- 
tively slender, strongly convex anteriorly, sharply conical, and with 
slender, delicate, longitudinal striz, except on the outer, anterior 


16 i FieLp CoL_umBian Musteum—Geotocy, Vou. II. 


part, where the surface is nearly smooth. The posterior teeth are 
much smaller, as already stated, and are much more closely placed, 
their length varying from six to twelve millimeters. 

The united farieta/s form a high, thin, vertical plate of bone, 
convex in outline, about fifty millimeters in height in the middle, and 
only three or four in thickness at the margin, and extending nearly as 
far forward as the pineal foramen. Posteriorly, the sides extend 
downward and outward into a broad flattened process for union with 
the upper ramus of the squamosal. The suture, which is clearly 
apparent, runs downward and outward to the free margin of the 
parietal on each side, beginning in front of the posterior thickened 
bar of the squamosal. Anteriorly this free margin of the parietal is 
continued outward, like the eaves of a roof, to the posterior part of 
the orbit, where it is somewhat roughened; it turns upward here 
rather abruptly. About twenty millimeters above this angle, separated 
by a concave space, is the massive projection for the epipterygoid. 
This bone has been broken away from its attachment on each side, 
and separated for a short distance, leaving a jagged fracture, without 
indications of suture. The upper margin of this thickened epiptery- 
goid protuberance is continued by sutural union with the postfrontal. 
A little in front of the parietal foramen, the bone narrows to a width 
of four or five millimeters, blended with and continued into the frontal, 
which continues forward to the premaxillary, under which it disap- 
pears. The sutural union for the postfrontal is well marked on the 
right side, beginning a little back of the pineal foramen and running 
downward, outward and backward to the upper margin of the epiptery- 
goid protuberance. Internally the parietals form a broad roof, to 
which is attached, rather far forward, by distinct, oval, obliquely 


placed, V-shaped articular surfaces, the paired supraoccipitals, which | 


do not reach quite to the lower free margin of the parietals on 
each side. | 

Anteriorly, as already stated, the frontal (?) continues, without 
the slightest indication of a suture with the parietals, forward for forty 
millimeters or so more, as a narrow, flattened surface above, distinctly 
divided by a median suture, to the upper end of the facial processes 
of the premaxillz, which articulate on the outer side of the slender 
projection, overlapping the upper surface. How much further the 
bones continue I can not say, but evidently as far forward as the 
anterior end of the orbits. On the right side, the ‘‘ postprefronto- 
nasal” has been macerated away, so that its relations are clearly 


marked. Below these bones are broader, continuous on each side. 


with the free margin of the roof, as already described. The rostrum 


Apr. 1903. NorrTH AMERICAN PLESIOSAURS—WILLISTON. 17 


formed by the ‘‘frontals”’ is stout and rounded, and is continued at 
least as far forward as the anterior end of the orbit, clearly separated 
above and below by the median suture. The anterior ends are lost in 
front in the broken fragments of bone, between ‘and beyond the 
anterior end of the orbits. Lying between the orbits, and separated 
from each other by a narrow interval, are the narrow bones which may 
represent the conjoined postfrontals and prefrontals and nasals. On 
the right side, as stated above, the bone had been macerated away, 
and while some of its processes had been broken off and lost, the 
sutures for union with the parietal, frontal and prefrontal are beauti- 
fully preserved, showing the relation to these bones in a way that 
precludes doubt. The bone shows no trace of division whatever into 
its supposed elements. It articulates with the ‘ frontal,” parietal, 
epipterygoid, ‘‘ postorbital,” ‘‘supraorbital,” ‘premaxilla and maxilla. 
Posteriorly the bone extends downward, outward and backward to the 
upper margin of the epipterygoid protuberance; externally and 
posteriorly it sends off a projection for union with the post-orbital ; 
anteriorly the bone fits into a groove on the outer side of the facial 
processes of the premaxillaries for a distance of thirty or forty milli- 
meters, and has a stout process on the outer side for union with the 
supraorbital, or whatever the element may be here. On the under _ 
side there is a broad, flattened, vertical plate, continuous from the 
posterior, inferior angle, and widened in the middle so as to-reach the 
greater part of the way to the upper surface of the palatal bone, form- 
ing the inner wall of the orbit in large part. The plate given off for 
union with the “supraorbital” is separated by a sharp, deep notch 
from a similar process for union with the ‘‘ postorbital.”” The ‘‘supra- 
orbital’? bone has been crushed back over this process, so that the 
distinguishing suture can be perceived in one place only, anteriorly. 
In front of the orbit, the bone sends out a thin, triangular plate, 
which curves downward to meet the maxille, separated from its mate 
by the premaxille. Doubtless this part represents the nasal, and per- 
haps also the lachrymal, but there are no indications of distinguishing 
sutures, and I do not believe that the nasal exists as a separate ele- 
ment in the adult plesiosaur—I can not find that it has ever been 
described in any plesiosaur. It joins the maxille broadly and the 
‘‘supraorbital” behind; in the angle between the three bones is 
located the small external nares. Below the supraciliar plate, near 
the anterior part of the orbit, on the side of the prefrontal, there is a 
well-defined fossa, leading forward into the ethmoidal region, into 
_ which opens a small foramen from the upper surface between the pre-. 
frontal and supraorbital. 


“ 
a 


18 FieLp CoLuMBIAN MusEUM—GEOoLOoGy, VoL. II. 


The supraorbital forms, as already stated, a horizontal plate 
extending out over the orbit in front. Its union with the prefrontal 
posteriorly is obscured by fracture, but indications of a suture are 
seen anteriorly. Between this bone and the postorbital there is a 
deep notch, angulated externally. The suture between the prefrontal 
and supraorbital is clearly seen anteriorly, running from the small 
foramen already mentioned forward and outward to terminate near 
the maxilla, at the posterior end of the nares. The connection of the 
bone with the maxilla can not be made out, as there has been an 
infolding here; its connecting suture with the ascending process of 
the maxilla is, however, well defined, running obliquely forward. 
The descending plate of the supraorbital has, in its orbital margin 
near the upper part, a small foramen, piercing the bone obliquely. 
The horizontal portion terminates anteriorly by sinking to the surface 
of the descending portion. The whole bone reminds one of the pre- 
frontal of Clidastes. : 

The fostorbita/ bone is a narrow, elongate and thin bone, united 
above with the postfrontal, and to a slight extent with the parietal, 
near the top of the epipterygoid; below to the jugal. On the right. 
side, this bone, like the postprefrontal and jugal, has been macerated 
away, and, although somewhat distorted, presents no evidence of 
being composed of more than one element. 

In the above description of these frontal elements, I have foie 
lowed the usual determinations, but I am not satisfied withthem. The 
‘‘supraorbital,”” though occupying the position usual for this bone 
above the orbit, has relations anteriorly that are altogether unusual; 
the nasal and the lachrymal do not appear to exist as independent 
elements. It would seem more likely that this supposed ‘‘supra- 
orbital” is really the lachrymal, if the postfrontal and: prefrontal are 
fused into one element. Again, such a combination of the postfrontal 
and prefrontal and their peculiar articulations is remarkable. The 
very narrow frontal, while showing a distinct suture in the middle, 
presents no evidence of any connection with the parietal —it seems 
more to be a very narrow rostrum projecting in front of the parietal 
and separating the bones, which otherwise would answer very well 
for frontals. In this latter case, the so-called ‘‘supraorbital” would 
really be the prefrontal, and the postorbital the postfrontal or post- 
fronto-orbital. This may seem a violent supposition, but it does not 
seem at all improbable to me. Nor is the union of the parietal with 
the premaxilla any more extraordinary than is the union of the supra- 
occipital with the frontal in many Cetacea. 

Sclerotic plates are present in the left orbit of this specimen in a 


Apr. 1903. NORTH AMERICAN PLESIOSAURS*-WILLISTON, 19 


nearly undisturbed condition. There are fourteen in the ring with 
beveled and imbricated contiguous margins, in texture, size and 
_ position very much like the corresponding bones of the mosasaurs. 
The pupillary opening measures about thirty millimeters in diameter, 
and the entire diameter of the ring is about seventy millimeters. The 
occurrence of sclerotic plates in the plesiosaurs has long been known. 
I described them in Cimoliasaurus snowiti in 1890, and Owen many 
years earlier (Fossil Reptilia of the Liassic Formation, p. 10) said: 
‘‘In both orbits some of the thin sclerotic plates of the eyeball are 
preserved ; this is the first specimen in which I have had evidence of 
their structure.” 3 

The juga/ is a small element intercalated between maxilla, post- 
orbital and squamoso-prosquamosal. The suture separating it from 
the maxilla runs nearly parallel with the lower border of the bone. 
_ In its posterior third this suture is very distinct; it seems to be con- 
- tinued forward to attain the margin of the orbit at its lower posterior 
part. Above, the bone is distinguished from the postorbital by a 
nearly parallel suture; behind by a nearly transverse suture from the 
squamosal. On the right side, the jugal had been separated from the 
other bones by maceration; its relations, therefore, are positively 
indicated. The bone terminates about twenty millimeters before the 
posterior end of the maxilla. On the inner side, just back of the 
rounded orbital margin, the bone articulates by a flattened surface, 
about the size of one’s finger-nail, with the ectopterygoid. -The bone 
is pierced on its outer surface by three or four small zygomatic 
foramina. ’ 

The broad, triradiate element, variously considered as being com- 
posed of, or the homologue of, the squamosal and mastoid by Owen*, 
the squamosal and supratemporal by Andrewst, the squamosal and 
prosquamosal by Owen and Baur, the supratemporal and supramas- 
_toid by Cope}, the squamosal, supratemporal and quadratojugal by 
Woodward§, differs materially in its structure from that described or 
figured in other plesiosaurian skulls, in that the element, or elements, 
whatever they are, articulate proximally with the maxilla, as well as 
the postfrontal and jugal. Posteriorly, the suture separating the.bone 


* Trans. Geol. Soc. Load. (2), v, pt. iii, pl. xlv, 1840. 

+ Quart. Journ. Geol. Soc. Lond. lvii, 249, 1896. 

t Proc. Amer. Phil. Soc. xxxiii, 110, 1894. Cope, in his essay on the posterior cranial arches in 
he Reptilia (Trans, Amer. Phil. Soc. 1892), reaches the conclusion that the lower temporal bar of 
he Crocodilia, SAhenodon, etc., corresponds with the zygomatic arch of the mammalia, and there- 
ore suppresses the term “ squamosal.’’ The squamosal—so-called—in the Reptilia he calls the 


_ : upramastoid, absent in the lacertilia and other forms. 


§ Vert. Paleont., f. 116 A, 1898, 


20 Fretp Co_tumMpran Museum —GEovoey, Vou. II. 


from the quadrate is situated as in Crmoliasaurus snowit, at the external 
angle of the quadrate, which it borders to its upper extremity., At 
the lower extremity there is a very distinct squamate suture, running 
upward and forward and becoming lost about twenty millimeters from 
its origin. This suture is clearly apparent on the two sides, and is 
also seen in the skull of C’moliasaurus snowiti, as it was figured by 
myself (l.c.) and Cope*. Just what the course of the suture is 
anteriorly I cannot say, but I believe that it is indicated by a line 
passing forward to the maxilla, and excluding that bone from union 
with the squamosal. Whatever be its relations anteriorly, I doubt 
not that the quadratojugal exists as a distinct ossification in the 
plesiosaurs. In a separated quadrate of another species of plesiosaur 
(Z. anonvmum WNill.), from the Benton of Kansas, the sutural sur- 
faces for union with the quadratojugal and squamosal are clearly dis- 
tinguished. The quadratojugal does not enter into the formation of 
the condylar surface of the quadrate, as has been suspected, and as it 
does in Sphenodon,; this is certain. On the outer side of this quadrate, 
just above the articular surface, there are two sutural surfaces—one 
on the posterior and outer border, for the attachment of the squamosal, 
the other on the anterior border for the attachment of the quadrato- 
jugal, which, in this case, as also in Dolichorhynchops osbornt, must 
have been overlapped in part by the squamosal. In Crmoliasaurus 
snow’, the suture between the squamosal and the quadratojugal is 
very clearly indicated from the exterior, the squamosal not descend- 
ing as low as in the other species. The suture shown as separating 
the quadratojugal from the squamosal anteriorly is conjectural, but I 
believe, as already stated, that it will be found to extend as. far for- 
ward as the maxilla. 

The suture separating the squamosal from the postorbital is short 
and vertical, joining the border near the anterior extremity of the 
bone, as seen from the outer side. The suture joining the jugal is a 
squamous one, extending on the inner side nearly to the margin of the 
orbit, but leaving a small space for the union of the ectopterygoid 
with the jugal. The suture with the maxilla is long and oblique, con- 
cealed.in about half its extent by the jugal. I believe, however, that 
the squamosal is really separated from the maxilla by the intervention 
of the quadratojugal, as already described, and for which there seems 
to be some evidence in the specimen. On the right side the maxilla 
had been removed by maceration, leaving the sutural surface for the 
temporal element very clear in its whole extent. 

Posteriorly, the sutural line of the squamosal passes downward 


* Proc. Amer. Phil. Soc. 1894. 


Apr. 1903. NortH AMERICAN PLESIOSAURS—WILLISTON. 21 


by a somewhat zigzag line to reach the inner border of the quadrate a 
little above the border of the pterygoid process. On the inner side, 
the sutural line passes nearly directly across, and then upward to the 
inner border. 

Fe The connection with the parietal is definite. The suture indi- 
cated by Cope in his figure of Cimoliasaurus snowitl (1. c.) does not 
exist in the specimen figured, nor is there any such in the skull of 
Dolichorhynchops osborni here described. In order to definitely deter- 
mine this fact I removed the portion supposed by Cope to be the 
supramastoid from the skull of the Cimodiasaurus specimen and carefully 
cleaned it, thereby proving beyond peradventure that the supposed 
suture is in reality a fracture. The squamosal, or as it should be 
called, the squamoso-prosquamosal, in that form, as will be described 
hereinafter, reaches to the top of the skull, notwithstanding Baur’s 
opinion to the contrary... The two squamosals touch each other, or 
nearly do so, as in the skull of Cryptoc/idus described by Andrews. 

The temporal bar in the plesiosaurs, it is thug seen, is composed 
of the jugal, quadratojugal, squamosal and prosquamosal (supratem- 
poral). This last element is not distinct in either of the skulls here 
described, nor is it usually apparent in the adult skull, but Owen* 
describes and figures it as distinct; Andrews also says} that ‘‘ In sev- 
eral Plesiosaurian skulls in the British Museum the suture between 
these elements is distinct.” 

The guvadrate is a short and broad bone, united by a pit-like 
sutural surface on the inner side with the posterior prolongation of 
the pterygoid, on the outer side with the squamosal and quadrato- 
jugal, as already described. Posteriorly the sutural surface for the 
squamosal begins a little above the pterygoid articulation, runs down- 
ward and outward for a short distance, then upward and outward to 
another point, whence it goes downward to appear on the outer sur- 
face a little below the angle of the bone, which it follows nearly to 
the lower articulation. The articulation for the paroccipital is imme- 
diately above and before the pit for the articulation of the pterygoid. 
A separated quadrate of another species (7. anonymum), already 
described in part, with its sutures distinct and the bone undistorted, 
shows an elongated articular surface, broadest upon the inner end, 
narrowed and turned upward at the outer extremity nearly to the 
lower end of the squamosal articulation. A non-articular groove on 
the inner side of the middle behind divides the articular surface; it 
does not appear to be present in either of the other species. The 


*Trans. Geol. Soc. (2), v, Pl. xiv (1840). 
ft Quart. Journ. Geol. Soc. lii, 250, 1896. 


22 - Fretp CoL_umpian MusrumM—Geovoey, Vot. II. 


pterygoid articular surface reaches to within about twenty-five milli- 
meters of the articular extremity. The inner border of the pit is 
produced forward for articulation, apparently, with the paroccipital. 
The two narrow, concave, articular surfaces for the squamosal and 
quadratojugal are separated by a narrow, non-articular ridge. They 
both extend very nearly to the cotylar surface of the bone. 

The fterygords articulate posteriorly by a deep, pit-like suture 
with the inner side of the distal extremity of the quadrate; the latter 
does not send out a process to meet the bone. The bar connecting 
the quadrate with the body of the bone is oval in cross-section, with 
a rounded inferior border. It is about thirty millimeters in length 
and is placed obliquely; it does not extend much posteriorly to the 
coronal plane of the occipital condyle. In front of this quadrate 
process there is an elongate, flattened or concave plate, with nearly 
parallel sides, separated from the parasphenoid bya slender, elon- 
gated vacuity.* At-the posterior extremity of this plate there is a nar- 
-row bridge connection with the basisphenoid. The connecting suture 
is not determinable, so that one cannot say whether the two ptery- 
goids meet here in the middle, as in Pe/oneustes and Pliosaurus, or are 
separated, as in Plestosaurus. In front of the interpterygoid vacuity 
the pterygoids unite with the parasphenoid broadly; here also the 
connecting suture cannot be determined. Opposite this connection 
exteriorly, the bone sends out a stout process for union with the ecto- 
pterygoid or transverse bone. Back of both of these, and on the inner 
side, near. the margin of the vacuities above, there is the attachment 
of a stout epipferygoid pillar, passing upward, and apparently a little 
inward to unite with the lower anterior part of the parietals, as 
already described: both extremities are tumid, and the connecting 
sutures cannot be determined. The rod is broken on both sides in 
the specimen near the parietal end, and, as preserved, is curved for- 
ward. It is oval in cross-section, with the greater diameter of about 
ten millimeters; the entire length is thirty millimeters. Anteriorly, 
the pterygoid sends a flattened process to meet the posterior extremity 
of the vomers; it is flattened and pointed. This process is gently 
expanded at each extremity, especially the proximal; it has a smooth, 
thin edge on each side, except at the distal end, where it meets its 
mate, suturally, in the middle. Between the two processes there is 
an elongate, oval vacuity, which is not filled by the ossified para- 

* Andrews calls this opening the posterior palatine vacuity or foramen; but this term is more 
properly restricted to the opening between the palatine, pterygoids and maxille, corresponding to 


the posterior palatine foramina of mammals, and is thus used in the Chelonia—the sub- or infra- 
orbital vacuity of Andrews and other authors. ; 


eR sea 
CaM, ce 


Apr.1903. NortH AMERICAN PLESIOSAURS—WILLISTON. 23 


sphenoid in this specimen. There is, however, a slight projection in 
the middle of the opening behind, which may represent. a more 
extensive ossification, but it seems very probable that there was a 
real vacuity here, unlike the condition in Pe/oneustes and Plestosaurus. 
The union with the vomer is oblique, from without inward and 
forward. 

The palatine and ectopterygoid on one side, though retaining 


Fig. 1. Fig, 2. 


Palate of Peloneustes. Palate of Plesiosaurus. 


Px., premaxilla; mx., maxilla; v.,.vomer; é., internal nares; fa., palatine; A7., pterygoid; 
f#v., posterior palatine vacuity; ¢f., ectopterygoid; 4s., basisphenoid; d0., basioccipital; g., quad- 
rate; sg.,squamosal, After Andrews. 


their original positions approximately, were free in the specimen ; 
they are complete and show their sutural relations very well. On the 
other side, they are both in position. The palatine is a long, narrow, 
thin bone, concave from side to side above, and correspondingly con- 
vex below. The inner, slightly sinuous margin is thin, and overlaps 
the outer margin of the palatine process of the pterygoid. Near its 
anterior extremity there is a small emargination for the nares*, where 


*See description of the palate in Brachauchenius beyond. 


24 FieLp CoLumpian MusEuM—GEoL_ocy, VoL. II. 


the bone comes in contact with the proximal end of the vomer; for a 
little distance in front of this emargination, and distad to the pointed 
extremity of the bone, the border is slightly thickened for union with 
the vomer. Posteriorly, the rounded extremity of the bone is slightly 
thickened, and with sutural roughening for union with the ectoptery- 
goid process of the pterygoid. The outer border is slightly concave 
throughout nearly its whole extent; it is also thin for nearly its whole 
extent. Anterior to the small narial emargination, the bone forms a 
long, slender point. On the proximal end, the thin border is under- 
lapped by the thin anterior prolongation of the ectopterygoid for a 
distance of about fifty millimeters ; the remainder of the extent comes 
in contact with the maxilla, but presents no distinct sutural surface, 
unless it be near the anterior extremity. There is no posterior pala- 
tine foramen. 

The ectopterygoid or transverse bone is of a slender, triangular 
shape. Its slender anterior end extends forward on the outer margin 
of the palatine. * The posterior inner angle has a well marked sutural 
surface underlapping the pterygoid process. The outer extremity is 
thickened, curving somewhat downward to unite with the jugal, and, 
by a thin border, with the maxilla. 

The vomer is a very long, narrow bone, uniting with the palatine 
process of the pterygoids posteriorly by a squamous suture, and, for 
a short distance on the outer side posteriorly, with the slender 
pointed extremity of the palatine, the small narial opening intervening. 
They le closely side by side, apparently without sutural union. 


They are concave above, and convex below from side to side, and are _ 


rather stout. The anterior ends are so concealed that they can not 
be described or figured. 


Brain-case.—The lateral walls of the brain-case in the reptilian 


skull are composed of six distinct elements, according to the views of - 


some comparative anatomists. Two of these may be fused with con- 
tiguous elements in the adult skull, or one or more of them may be 
entirely absent. Those elements supposed to contain the otic capsule 
were called by Huxley, in his lectures on the structure of the verte- 
brate skull (Elements of Comparative Anatomy, 1864), the epiotic, 


proétic and opisthotic. The other three are the supraoccipital, - 


exoccipital and alisphenoid. The epiotic, Huxley homologized with 
the so-called epiotic of fishes and batrachians, and, although indis- 
tinguishably united with the supraoccipital in all adult reptilian 
skulls*, he believed to be a distinct ossificatory element. This has 


* Parker describes the epiotic as a distinct element in 7yofidonotus natrix. Phil. Trans., 
1878, p. 403. 


‘Apr. 1903. NorrH AMERICAN PLESIOSAURS—WILLISTON. 25 


been denied by Baur*. No indications of such an ossification have 
been found in adult reptiles, living or extinct, even in those in which 
the opisthotic remains as a permanently free ossification. The opis- 
thotic was previously called paroccipital by Owen in 1838, and the 
name must take precedence. Copet, however, suspected that the 
opisthotic or paroccipital is really composed of two elements, the 
outer of which is the true paroccipital, while the inner, that entering 
into the formation of the otic canals, may be properly called the opis- 
thotic. Baur denies this, insisting that there is but a single element, 
persistent in the Testudinata, Ichthyopterygia, the young of Sphenodon, 
and other Rhynchocephalia, as well as in some of'the Cotylosauria ; 
firmly and indistinguishably fused with the exoccipital in all other 
reptiles, so far as is known; free, according to Cope, also, as the 
so-called squamosal of Baur, the paroccipital of Cope, the supratem- 
poral of Woodward, in the lacertilia. 

If there be but one element here, and, so far, the evidence is 
inconclusive that there are two, then it must be called the paroccipital, 
a name first given to it by Owen. Andrews describes the element as 
distinct in the young of Crvpfoclidus§, but there are no indications of 
it in the present specimen. 

The prodtic of Huxley, the alisphenoid ot Owen (Comparative 


* Zool. Anzeiger, No. 296, 1889; Journ. Morphology, 1889, p. é. 


+ The opisthotic in reptiles is generally early fused with the exoccipital, but in the Ichthyop- 
terygia and Testudinata it is distinct, and takes the place of the petrosal as a support for the quadrate 
in conjunction with the exoccipital. In the Pythonomorpha a bone which occupies the position of 
the terminal part of the opisthotic (or paroccipital, which is the older name) issues from between 
the exoccipital and petrosal, and sifpports the quadrate. Whether this is homologous with part or 
all of-the paroccipital is an open question. For the present I call it the paroccipital and it is 
probably a distinct element from the opisthotic.’’ Cope, Syllabus, 2d ed., 1898. <A fuller description 
of the relations of this bone the reader may tind in my paper on the Mosasaurs (Univ. Kansas Geol. 
Surv., vol. iv, p. 121). After much reflection I believe that Cope is right in rejecting the term squa- 
mosal for this element, whatever it is. Parker describes and figures the opisthotic as a large ele- 
ment in the snake (I. c.), occupying its usuai and normal position, At the same time it is exceed- 
ingly difficult to believe that the remarkable relations of the bone in the mosasaurs can be those of 
the squamosal, occupying almost the normal position of the real opisthotic. That the bone called 
the prosquamosal in the lizards is not the squamosal would also seem probable, though not 
impossible. 1 prefer to call the elements, until it be proven that there are two opisthotics 
in the lizard, the paroccipital and prosquamosal with Cope. It is of interest to note, however, that 
Cope, in his last edition of the Syllabus (published posthumously), retains the name of squamosal 
for the element he previously called the supratemporal (7. ¢., the prosquamosal). Further on he 
defines the plesiosaurs as follows: ‘‘ No supramastoid; paroccipital not distinct; a quadrato jugal 
arch; scapula triradiate; no clavicle; ribs one-headed.”’ Cope’s supramastoid is the bone he thought 
erroneously to exist in the skull of Cimoliasaurus snowii, that is the real squamosal if present, and 
Andrews assures us that it is sometimes present in the young animal, Ido not understand what is 
meant by ‘‘ no clavicle,’* unless it be that he accepted Hulke’s determination of these elements as 
the omosternum, a subject which will be discussed further on. He forgets also that some plesio- 
saurs do have ridimentary double-headed ribs in the cervical region. 

Notwithstanding all that has been written, the homologies of the temporal bars in the reptilia 
are yet uncertain, more so than any other parts of the reptilian skull. 


t Vertebrate Paleontology, 1898. 
§ Geological Magazine, 1895, p. 242. 


26 Firtp Co_LumBiAN MustumM—GEoLocy, VoL. II. 


Anatomy), is the petrosal of earlier authors, about which there is now 
no discussion. It always articulates behind with the exoccipital and 
paroccipital, above with the supraoccipital, below with the basi- 
sphenoid, and to a greater or less extent with the parietal (in certain 
lizards, etc.), the alisphenoids, when present, and epipterygoids. 
The epipterygoid, the columella of earlier authors, unites the ptery- 

goids with the parietals or frontals. It has been supposed to be 
identical with the alisphenoids by Baur and others, but Baur* later 
retracted this opinion, with reason, as may be seen by an inspection 
of the cranial walls of Sphenodon. 

The alisphenoids (orbitosphenoids of Owen) articulate with the 
basisphenoid below, when present, and with the petrosals behind. 
In the crocodilia and Sphenodon they also articulate with the epiptery- 
goids. ‘They seem to be absent in the plesiosaurs. : 

The bones of the brain capsule in our specimen of Dolichor hyn- 
chops had been separated by maceration before fossilization, and were 
more or less displaced and entangled with one another. Moreover, 
in each temporal vacuity there had lodged deeply a thoracic vertebra, 
wedged in and causing more or less distortion of the temporal arches. 
The atlas and axis, also, were crowded into the occipital region. 
The vertebree had to be sacrificed in order not to endanger the other 
bones. Mr. Martin, with great care and patience, removed the 
disassociated bones of the capsule in more or less completeness. 
_ They were all soft and mealy, almost of the consistency of brown 
sugar when wetted, but by carefully infiltrating them with a solution 
of gum arabic, the bones were hardened bit by bit and then removed 
from the matrix. This exposed the surface of the basioccipital and 
basisphenoid in their entirety, in an undisturbed and uninjured con- 
dition. A gelatine mould of this surface was then made, from which 
a plaster cast was taken, showing the sutural surfaces for the exoccip- 
itals and petrosals. While none of the bones were obtained quite 
complete, yet the mates, for the most part, mutually indicate the 
complete characters of each, thus enabling a nearly complete restora- 
tion of the capsule to be made. And the results have been well 
worth all the trouble, as the bones present certain features of much 
interest. 

The brain cavity is broadly open in front, as in the lizards} and 
Sphenodon, with a broad base on the basisphenoid, a deep depression 

* Zool. Anzeiger, No. 298, 1889. 

+In the Pythonomorpha I have recently discovered that the brain-case is bounded in front in 


part by a well developed orbitosphenoid, uniting the frontal with the basisphenoid, The same bone 
is present in the lizards and snakes. See Bulletin Kans. Univ., 1, No.9, p. 14. 


- Apr. 1903. NorrH AMERICAN PLESIOSAURS—WILLISTON. 27 


for the pituitary, a narrow roof under the parietal, an open vacuity 
posteriorly in the supraoccipitals, and with a relatively large otic 
capsule. The exoccipita/s unite obliquely with the basioccipital, tak- 
ing no part in the formation of the condyle. The paroccipital pro- 
cesses are small and slender, and there is no indication of a distinct 
ossification. They are dilated slightly at the extremity, where they 
abut against the upper part of the quadrate. They are directed down- 
ward and. outward, the distal extremity reaching a level below the 
top of the occipital condyle. The occipital foramen is transversely 
oval, if the upper end is assumed to be near the top of the exocci- 
pitals, which.show a slight angularity at the place of their union with 
the separated supraoccipitals. At 
the upper posterior extremity of 
each exoccipital there is a small, 
deeply excavated, angular cavity, 
excavated almost wholly from the 
exoccipital, its upper border only 
touching the posterior.angle of the 
supraoccipital. Itsexcavated sur- 
face is smooth and sharply angu- 
lar, looking upward and inward. 
This surface probably corresponds 
to the smooth tendinous surface 


seen on the outer angle of the supra- 
occipital, extending slightly on the 
corresponding angle of the exocci- 
pital, in the crocodile. At the 
posterior part, the exoccipitals 


Fig. 3. 


Dolichorhynchofps osborni. Occipital view of 


skull. x %. Fa., parietal; sg., squamosal; g., 
quadrate; so., supraoccipital; .¢0., exoccipital; 
fi., pterygoid; oc., occipital condyle; éo., basi- 
occipital. 


approach each other rather closely, 

leaving about four millimeters of basioccipital space in the circumfer- 
ence of the foramen magnum. Anteriorly, however, the two bones 
diverge rather widely, terminating a little posterior to the suture 
separating the basioccipital from the basisphenoid. On the inner 
side, back of the middle of the bone, and a third of the distance above 
the sutural margin, is the large oval foramen for the vagus, opening 
exteriorly below the middle of the moderately expanded paroccipital 
process. The smaller foramen for the hypoglossal is situated mid- 
way between this and the posterior margin, and nearer to the sutural 
surface; it opens near the vagal orifice. The sutural surface for the 
supraoccipital is flat and’ broadly triangular, pierced near its middle 
by a small foramen leading into the posterior semicircular canal in 
the supraoccipital, the floor of which is seen on this surface, leading 


Ae 
28 FigeLp CoLuMBIAN _MusEuM—GEOoLoGy, VoL, II. 


as a narrow groove to the inner posterior margin of the surface. 
Posteriorly the slit for the eighth nerve seems to bé a little above 


‘and back of the vagal opening, in the interstice between the exoccip- . 


ital and petrosal. The large cavity of this bone looks backward to 
communicate broadly with a similar cavity in the petrosal on the inner 
side. On the outer side there is a small foramen, nearly or quite 
separated from the inner opening, also communicating with a small 
foramen in the opposed sutural surface of the petrosal. Externally 
the exoparoccipital shows a narrow fossa below the process, into 
which open the vagal and hypoglossal foramina. Above, the gently 
convex surface continues into the similar surface on the sides of the 
supraoccipitals. The posterior borders of the exoccipital and supra- 

occipital meet in an obtuse angle, which is excavated, as already 
‘ described for ligamentous attachment. 

The swpraoccipitals are not only parial, but they are widely 
separated from each other, approaching each other only at the upper 
extremity posteriorly. They enclose between their smooth, narrow 
edges posteriorly a large vacuity, continuing the foramen magnum 
quite to the parietal roof. This relation of these bones I can not 
find paralleled in any reptiles. Though paired in the Stegocephalia, 
as also in Pariotichus, they meet in a median suture. Whether this 
peculiar structure obtains in all other plesiosaurs I can not say, 
inasmuch as the only references to the supraoccipitals which I find 
in the literature is a brief one by Andrews* concerning the bone in 
the young of Cryftoclidus, in which nothing is said of a similar 
structure, and a notice by Owent+, who describes the supraoccipital 
in Plesiosaurus dolichodeirus as a single, arched bone. 

The inferior articular surface for union with the exoccipital is flat 
and triangular in shape, looking downward or slightly backward. It 


is pierced near its middle by the foramen for the superior semicircular 


canal. The sutural surface for union with the petrosal meets the 
exoccipital at an angle of about one hundred degrees, and is flattened 
or gently concave, and shorter than the other sutural surface. The 
external surface is moderately convex, and a little roughened. The 
posterior border is thin and smooth, deeply concave and sinuous, the 
upper extremity curved inward. The inner surface is quite smooth, 
gently convex from before backward, nearly straight to its upper 
third, where it bends strongly inward. The posterior border is short, 
thick, convex from side to side, and concave on its upper part before 
joining the sutural surface. The sutural surface above, for union with 


*Geol. Mag. 1895, p. 242. 
+ Fossil Rept. Liassic Formation, p. 8. 


* 
a 


Apr. 1903. NORTH AMERICAN PLESIOSAURS—WILLISTON. 29 


the parietal, is elongate oval in shape, slightly convex in both direc- 
tions, and turned obliquely inward posteriorly, so that the two bones 
when in place form aV. The surface looks forward and upward, and 
joins a projecting sutural surface of like shape on the parietal bone. 


Manpiste.—F rom the exterior of the mandible four elements are 
visible, arranged much as in the crocodile or Sphenodon. The dent- 
ary extends far back along the upper border, quite to the top of the 
coronary eminence. Thence its suture runs obliquely to a little 
beyond the posterior end of the symphysis on the lower border. The 
element back of this on the upper border is doubtless the surangular, 
separated from the angular below by a suture placed very much as it 
is in the crocodile, beginning at the extreme posterior end of the 
mandible. The bone extends anteriorly as an elongated point between 
the dentary above and the angular below. The suture separating the 
element fram the articular cannot be made out. The two, united, 
agree quite with the element described by Guenther in Sphenodon, and 
as seen in a specimen fifty-eight millimeters in length before me. | 
distinguish in this mandible, as did Guenther in his, only four elements 
—the dentary, which reaches far back; the coronoid, a flat triangular 
bone occupying its usual place; the articular, inclusive of the 
surangular; and the angular. Baur* describes five elements in a 
Sphenedon skull fifty-six millimeters in length. The articular he 
restricts to a small nodule or disk of bone, similar to that of the 
turtles, forming the articular surface; the surangular, the bone 
before the cotylus, which he indicates as separated by a suture; the 
angular he considers to be the inner prolongation of the bone which 
reaches to the coronoid. The slender bone usually called the angular 
he believes to be the splenial; while the bone usually called the 
splenial (presplenial, Baur) in the crocodile and lizard he believes to 
be wanting in the Sfhenodon, as it usually is in the turtles. The 
small ossification which he finds in the cotylus of the young 
Sphenodon, similar to the element in a like place in the 7estudinata, he 
assumes to be present in all reptilian mandibles, but is obliterated in 
the adult skull by the anchylosis of the suture. I certainly do not 
find such a bone in the Sphenodon mandible before me, nor could Guen- 
‘ther distinguish such an element. He believes then, that the element 
usually considered the articular, is in reality composed of two bones — 
a chondrogenous articular part and a dermogenous anterior prolonga- 
tion. This is probably true, but I do not see the necessity of chang- 
ing the names of the other anterior elements and of calling this 


* American Naturalist, 1891. 


30 FieLp CoLumptan MuseEuM—GEo ocy, VoL. II. 


anterior prolongation the angular, as does Baur. From the fact 
that the bone on the inner side of the dentary, covering Meckel’s 
groove, is the only one which can with propriety be called ‘‘splenial”’ 
(a ** bandage” or ‘“‘patch”), or opercular (a cover), it will be better to 
retain the former name for the element, as usually applied, and to 
give a new name to the part separated from the articular, wherever 
it exists as an independent bone; it may be called the prearticudar. 


Fig. 4. 


Right mandible of Clidastes tortor Cope. D., dentary; sf., splenial; fra., prearticular; ang., 


angular; cor., coronary; a@vt., articular; sz7., surangular. 


I assume that the element containing the cotylus must be the 
articular, and that the one in front of it, back of the coronoid and 
dentary, must be the surangular, though, as already stated, I can find 
no positive evidence of a separating suture in the present specimen, 
as is also the case in the adult Sfphenodon mandible. Doubtless in 
some more fortunately preserved specimen, or in one of a younger 
animal, the separating suture will be traced. I will add that the 
suture indicated by Cope* in his figure of the skull of Cimoliasaurus 
snowil, as separating the articular from the surangular, does not exist 
in the specimen; the place is indicated by a mere groove only. 

The angular is very long, and_is extensively visible from both 
within and without. On the outer side it is seen reaching to a little 
beyond the proximal end of the symphysis, where the pointed extrem- 
ity is visibly intercalated between the dentary and a small portion of 
the splenial. On the inner side, the suture follows inward below the 
cotylus to the anterior inner angle of the articulation, near which it 
passes upward to meet the prearticular. The bone passes beneath 
this latter,element but its connection with the surangular cannot be 
made out. Along the inferior border of Meckel’s groove and the 
splenial, the suture goes forward to near the proximal end of the 
symphysis. 


On the inner side of the mandible, there is an extraordinary 


arrangement of the bones. After much deliberation, I interpret them 


*Proc. Amer. Phil. Soc. 1894. 


Apr. 1903. NortH AMERICAN PLESIOSAVRS—WILLISTON. 31 


as the splenial (presplenial of Baur), the prearticular (angular of 
Baur), and the coronoid. The identity of the sf/enia/ is assured. It 
has been dislodged upward slightly, disclosing the narrow Meckelian 
groove, which terminates in an orifice at the proximal end of the 
splenial. The bone ends posteriorly below the coronoid eminence. 
Anteriorly it broadens so as to cover all but the upper inner part of 
this surface, uniting with its mate to form the symphysis. From 


Fic. 5, 


Left mandible tosymphysis of Dolichorhynchops osborni. art., articular; fra., prearticular; 
sur., surangular; cor., coronary; sf., splenial. Compare also PI. II. 


below, the thickened bone forms the inner part of the symphysis for a 
short distance forward, at least. How far it extends can not be deter- 
mined, as it gradually becomes thinner and disappears from view. 
(See Pio IT.) 

The bone which I determine as the coronoid.is most peculiar, 
remarkably unlike that in any other animal which I know. It is a 

long, slender, flattened, trihedral bone, extending far forward, and 

like the splenial, meeting its mate in the median symphysis. It 
extends as far back as the end of the dentary, along its inner side, to 
the most elevated part of the surangular, where it is thin and spatu- 
late. It follows the inner margin of the dental border of the dentary, 

_apparently at least as far as the middle of the symphysis. At the 
beginning of the symphysis with its mate, the bone is somewhat tri- 
angular in cross-section, with its thin margin below touching the 
splenial; the mesial surface is in contact with that of its mate, while 
the upper surfaceis narrow. On one side the bone, while still retain- 
ing its proper relation with that of the opposite side, has been par- 
tially dislocated from the mandible, so that there can be no question 
of its morphological relations to the contiguous elements.* 

Between the splenial and the coronoid, on the inner side, is 
seen a narrow, thin bone, corresponding quite to the dermogenous 
portion of the articular in the turtles and Rhynchocephalians, that is, 

 *This peculiar relation of the coronoid is well illustrated in fig. 13, p. 476, vol. xxxvii, of the 


Quarterly Journal of the Geological Society, in Prof. Sollas’ article on ‘“*A New Species of 
Plesiosaurus from the Lower Lias of Charmouth.” 


32 Fietp CoLumBian .MuseumM—GeEo ocy, Vo. II. 


the angular of Baur. It lies above the splenial, disappearing beneath 
the coronoid anteriorly. Posteriorly it is joimed by a suture with the 
articular, approaching but not quite entering into the cotylar surface, 
or if so, only to a slight extent. This end has been dislodged slightly 
from its normal position and is slightly twisted upward. It is 
scarcely possible that this is due to fracture, since the surface has all 
the indications of a suture, and a fracture could hardly have occurred 
here without injury to the bone underneath. The end is slightly 
‘thickened and fits into a pit on the anterior upper part of the articu- 
lar rim; just below the suture, separating it from the articular, there 
is a longitudinal ridge-like roughening, and a narrow, deep pit. This 
element I call the prearticular. 

For the sake of comparison, I have figured in Pl. V the mandi- 
ble of Sphenodon, Crocodilus, Chelydra, Varanus, with the interpretation 
of the elements as here accepted. 

The bones of the skull, as of the entire skeleton, seem to have 
had a sort of postmortem plasticity. Apparently during life the 
sutures everywhere were free, and the parts all readily separable, and 
wherever the bones have been disturbed or distorted the sutures have 
pulled apart and widened. Where there has not been such disturb- 
ance, however, the sutures are often obliterated, the elements fusing 
together. This would seem to indicate youth, but plasticity in the 


Cretaceous skeletons was largely due to the composition of the bones, - 


which may have been more or less persistent throughout life. Those 
in which the inorganic proportions were large have suffered less from 
postmortem disturbances than those in which the organic material was 
considerable. Bird bones were never plastic, and very rarely are the 
bones crushed, the cavities being filled with crystalline material often. 
Of the pterodactyls, however, the bones are invariably found crushed, 
though presenting little evidence of plasticity. Among the mosasaurs, 
the more firmly ossified bones of Cléédastes are less often changed in 
shape, while the Tylosaurs, on the other hand, were more or less 
subjected to a plastic distortion. The structure of the plesiosaur 
bones in all that I have seen is unusually soft. 


VerTesR@.—Atlas and axis. (Pl. XXII.) The az/as has the 
usual number of elements, the intercentrum and the two side pieces, 
or neurapophyses. It will be convenient, however, to describe in 
this connection the parts of the whole axial and atlantal complex, that 
is, in addition to the odontoid, the axial intercentrum and the axial 
centrum and arch. The arrangement of all these parts is very like 
that in the lizards, crocodiles and various other reptiles, save that the 


< 
ut 


Apr. 1903. North AMERICAN PLESIOSAURS—WILLISTON. 33 


structure is somewhat more primitive or generalized. The atlantal 
intercentrum is the largest element of the complex, save the axial 
centrum. It has five articular surfaces for union with as many bones ; 
four of these surfaces are sutural, and, doubtless in old animals or in 
other species, the sutures may be obliterated. The inferior or ventral 
surface has an obtuse ridge along the middle, on either side of which 
the surface is flattened cr a trifle convex. This surface is free, and 
its anterior and posterior margins are parallel. The anterior or 
_cephalic surface is concave for articulation with the hemispherical 
occipital condyle, its rim forming more than one-third of the entire 
circumference of the cup. The posterior surface is flat, elongated 
triangular in shape, with a V-shaped emargination, for articulation 
with the axial intercentrum. Dorsally the bone articulates by a 
broad sutural surface with the odontoid, except on the cephalic part 
of each lateral margin, which unites by a small, semi-oval surface with 
the neurapophysis. 

The axial intercentrum is not unlike the atlantal in shape, when 
seen from the ventral side, though smaller. Its ventral surface con- 
tinues the obtuse ridge of that intercentrum, but it is here quite 
prominent, the nearly square free surface on either side being dis- 
tinctly concave. The posterior surface for sutural union with the 
body of the axis is flat or gently concave; its free margin is broadly 
V-shaped, with the inferior angle rounded; the dorsal margin is 
gently concave in the middle to the truncated, very broad arms of the 
V. The cephalic sutural surface is flat, for union with the atlantal 
intercentrum, and like that of this bone, its surface is broadly tri- 
angular in shape. On either side the bone articulates, through the 
greater part of its extent, by an oblique, concave surface with the 
axial rib, forming part of the pit for the reception of that bone. Its 
upper lateral part unites by a small surface with the odontoid, form- 
ing with it and with the axis the complete margin of the rib-pit. 
Dorsally the bone articulates on its caudal half with ye axis; on its 
cephalic half with the odontoid. 

The odontoid, or atlantal centrum, unites posteriorly by a. broad, 
flattened, sutural surface with the body of the axis. On the cephalic 
side there is a concave surface in the middle, occupying about one- 
half of the diameter for articulation with the condyle, the deep cup 
being completed ventrally by the atlantal intercentrum and on the 
sides by the neurapophyses. Dorsally the neurapophyses leave a 
small notch of the rim incomplete, which is partly filled out by the 
odontoid, making the diameter of the cupped surface of this bone 
greater dorso-ventrally than from side to side. The sides of the bone 


34 Firtp Cotumpian Mus—EuM—GEoLocy, VoL. II. 


have a free, irregularly trapezoidal surface, the longer, cephalic bor- 
der articulating with the atlantal neurapophysis, the caudal, oblique 
border with the axial intercentrum, the ventrocaudal angle with the 
axial intercentrum, and the ventral part of the caudal border with the 
axial rib, its dorsal angle touching the axial neurapophysis. The 
ventral side of the body unites suturally with the intercentra. On the 
dorsal surface there is a narrow, free space, which helps form the 
floor of the neural canal. 

The /ateral pieces or neurapophyses are composed of a large body - 
for sutural union with the other elements, and a small, laminar, 
dorsal projection, which is free. The body is irregularly five-sided, 
the external free surface convex dorso-ventrally. The cephalic sur- 
face is smooth and concave, forming the lateral rim of the condylar 
cavity. Ventrally a small articular surface is for union with the 
condylar rim of the atlantal intercentrum; the border nearly parallel 
with the upper. Caudad, there is a small articular surface for union 
with the arch of the axis; the long border between these two joins ‘the 
lateral surface of the odontoid; the dorsal surface sends a flat pro- 
jection backward to touch, or nearly touch the small, vestigial 
prezygapophysis of the axis; this lamina is continued into a small, flat 
process, the vestige of the neural lamina. These neurapophyses are 
peculiar in articulating at their base for a short distance with the 
neurapophyses of the axis, doubtlessly corresponding to the articular 
surfaces between the body of the axis and the lateral masses of the 
atlas in the mammalian vertebre. It is very plainly evident, there- 
fore, that the name zygapophysis, when applied to this articulation in 
the mammalian axis and atlas is incorrect—the real zygapophyses are 
completely lost. ; i 

The atlas, as a whole, is of a primitive and generalized character, 
in that the neurapophyses are, for the most part, borne by their own 
centrum, and the atlantal arch only in small part by the atlantal 
intercentrum. : 

The axis has its anterior surface flattened for sutural union with 
the odontoid. On the cephalic ventral part is received the axial 
intercentrum, the lines of the union reaching midway of the body on 
the ventral side. The pit for the reception of the rib is very large and 
deep, and is formed in part by the odontoid and intercentrum. The 
pedicles of the arch are stouter and broader than in the following 
vertebra, articulating in front with the lateral pieces of the atlas, 
and, to a slight extent, with the odontoid. The prezygapophyses 
are represented by a small tubercle, approximated to the flattened 
posterior process of the lateral atlantal pieces. Back of this there is 


- Apr. 1903. NortH AMERICAN PLEsIosauRS—WILLISTON. 35 


a thickened, rugose, horizontal ridge, reaching to the intervertebral 

“notch. The posterior zygapophyses are situated rather high, and do 
not differ materially from the same processes in the following verte- 
bre. The spine is incomplete posteriorly, but seems to have been 
short, stout and much inclined. 

The structure of the plesiosaurian atlas and axis has been 
described by Owen,* Huxley} and Barratt.{ In the specimen of a 
Plesiosaurus described by Barratt the different elements were sep- 
arated and were for the most part complete. The neurapophyses 
differ markedly in their expansion inward to form a roof for the neural 
canal, though they do not touch each other. Theatlantal intercen- 
trum also differs in its posterior projection into ‘‘two long processes,” 
which are, however, broken away, leaving only their bases. The 
axial rib seems to articulate with the axis and axial intercentrum 
only. In Plesiosaurus etheridgii, the atlas and axis of which are 
described by Huxley, the bases of the atlantal neurapophyses are 
much larger and meet above the odontoid. In Plestosaurus pachyomus, 
as described by Owen, ‘‘the anchylosed bases of the neurapophyses 
form the upper border of the cup,” and the atlantal intercentrum 
‘«develops a thick but short rough tuberosity from its under part,” 
and the rib projects from the centrum of the axis only. The pro- 
cesses were all broken away. 

It is seen that the structure in Dolichorhynchops i is more special- 
ized than in these species of Plesosaurus. 

The atlantal and axial intercentra, variously considered by differ- 
ent authors as ‘‘subvertebral wedge-bones,” hypapophyses or hypo- 
centra, are correctly homologized by Baur,§ Albrecht|| and Osborn. { 
It is a little interesting to note, however, that Owen (I. c.) long ago 
gave a correct hint of their homology: ‘‘ According to the latter view, 
what has usually been regarded as the centrum or body of the atlas 
in Saurians, Chelonians and the higher Vertebrata, would be the 
hemapophyses of that vertebra; and the odontoid process the true 
centrum.’’ He concludes, however, that these elements are ‘‘ detached 
cortical parts of the real centrum; though later he correctly compares 
them with the hypocentra of the labyrinthodonts. 

Perhaps the most primitive and unchanged condition of these ele- 

* Ann. Mag. Nat. Hist. xx, 217, 1850. 

t Geological Journal, 1858. 

tAnn,. Mag. Nat. Hist. Nov. 1858. - 

§ American Naturalist, 1887, Sept., p. 8309. 


|| Bull. Mus. Roy. d’hist. Nat. de Belg. ii, 185. ; 
“| Mem. Amer, Mus, Nat. Hist. i, p. 157. . 


36 FreLp CoLuMBIAN MusrtuM—GEo ocy, VoL. II. 


ments in the reptilia is found in /chthyosaurus, in which, as shown 
in the figures given of the axis and atlas by Owen, the intercentra 
of the first three vertebra occupy nearly their normal and unaltered 
relations to the vertebra. It is difficult to understand, however, how 
such a primitive condition of these parts could have been inherited 
from a terrestrial ancestor. In the plesiosaurs the specialization has 
been carried further, still the structure is yet more primitive than is 
known in any modern reptiles and in most of the extinct. We cer. 
tainly can look for ancestral forms of these vertebre among the 
Stegocephalia or Anomodonts only; in all other reptilia they 
have acquired too great specialization to easily revert to the gen- 
eralized structure. 

In the modern crocodiles the specialization has been carried so 
far that the axial rib has become supported by the atlantal centrum 
only, while the atlantal rib has been pushed forward on the atlantal 
intercentrum, 

It is of interest to observe that in Shastosaurus of the earlier Ich- 
thyopterygia, according to Merriam, there were probably five inter- 
centra present in the anterior cervical region, while in /chthyosaurus 
there are but three, and in the more specialized forms, Baptanodon,* 
they have entirely disappeared. 

Beyond the axis there are seventeen distinctly cervical vertebre 
preserved, together with one or two transitional ones, which must be 
classed with the dorsals, however. I believe that these were all that 
the animal possessed, though it is possible there may have been one 
or two more. The arches and ribs of all, save of the third, were 
detached and scattered about among the other bones, so that much 
difficulty was encountered in properly associating the parts. Because 
of a gradual increase in size of the ribs and arches, as well as the 
centra, it would seem that the final collocation made is correct, and 
because all these processes agree in number it would seem still more 
probable that no vertebre are missing. (See Pls. VI-IX.) 

The centra increase in height and width gradually throughout the 
series. The third has a transverse diameter of thirty-five millimeters, 
a height of thirty and length of twenty-eight. The sixteenth centrum 
has its corresponding diameters as follows: forty-five, thitty-eight and 
twenty-six. The three following are somewhat distorted, but seem 
likewise to increase slightly in height and width. It will be observed 
that the length is nearly or quite the same in all, the differences being 
exhibited in the width and height only. The articular surfaces of the 
centra are gently and evenly concave, with a slight rounded eminence 


*W.C. Knight, 27 tt. 


sh* 


t Leoaen 


Apr. 1903. NortH AMERICAN PLESIOSAURS—WILLISTON. 37 


in the middle of the concavity, sometimes apparently obsolete. The 
margins are rounded, the cartilaginous borders limited exteriorly by 
a slender, smooth line. On the ventral surface, near the middle 
antero-posteriorly, there are two vascular foramina, at the bottom of 
a slight depression, and separated from each other by a rounded 
ridge. Posteriorly the distance between these foramina becomes 
greater. The pit for the articulation of the cervical rib occupies 
‘nearly the whole length of the centrum, between the cartilaginous 
margins, and reaches also nearly to the plane of the neural sur- 
face. The ribs increase in length and width from the axis to the 
beginning of the thorax. They are single headed, flattened, with the 
free extremity moderately dilated and thinned, except those of the 
axis, which are more styliform, and are directed more obliquely back- 
ward. On the following vertebre they are directed outward and 
backward, with the distal extremity rounded, except in those of the 
anterior vertebra, where the anterior part distally is slightly angu- 
lated, as though suggesting a rudimentary anterior projection. The 
spines slope gently backward. They increase but little in length, 
that of the third vertebra measuring forty-eight millimeters in length 
while that of the last is but fifty-five above the zygapophyses. They 
increase in stoutness, however, much more than in length, the ante- 
rior ones being slender, the posterior broad and thick with a some- 
what expanded cartilaginous extremity. The zygapophyses are 
broadly separated throughout, with an obliquity of about thirty 

_ degrees from the dorsoventral plane. They are broadly oval in out- 
line, of large size and nearly flat. They project strongly from the 
body of the vertebra, leaving a space of about ten millimeters in 
extent between the centra, when in close articulation, for the inter. 
vening cartilage. The diameter of the spinal canal throughout the 
series is about fifteen millimeters. Upon the floor of the canal there 
are two venous foramina, near the middle. 

Thirty dorsa/ vertebre were found in the matrix. The arches 
were invariably separated from the centra, and, because of the general 
resemblance of the latter it is impossible to say whetherall have been 
correctly associated. The centra were in large part crushed or com- 
pressed, and in some cases were so soft that it was found impossible 
to remove them entire. Two of the arches were wedged into the © 
temporal fosse of the skull in such a way that it was found necessary 
to largely destroy them in cleaning the skull. In general, the spines 
of the dorsal region were so soft and frail, intermingled as they were, 
that they could not be removed. A large part of them, hence, have 
been modeled in the restored skeleton. Because, however, of not a 


38 Fietp CoLuMBIAN MusgEuM—GEOoLocy, VoL. II. 


few arches that were recovered complete, or nearly so, from different 
parts of the series, the restoration of the intervening parts of the 
series has presented few difficulties. 

The spines decrease very slightly in height, in breadth and in 
thickness. Anteriorly they are directed somewhat backward, but 
soon become quite vertical in position. In the posterior cervical and 
anterior dorsal region the spines present a much larger, oval and 
truncate extremity for ligament or cartilage; this surface measures 
‘from twelve to fifteen millimeters in width in some of the posterior 


cervicals. In the posterior dorsals the extremity is narrow—three or: 


four millimeters in width. The first diapophysis* is small, for the 
attachment of a small, short rib, and is situated low down on the 
pedicle,} close to the sutural surface. The next is much stouter and 
longer, for the attachment of a long and strong ’rib. The next two or 
three ascend progressively on the pedicle, until in the fifth the upper 
margin of the root is above the plane of the anterior zygapophyses. 
They retain this position throughout the series, the last two or three, 
only, descending toward the centrum. The diapophyses have ac- 
quired their greatest length by the sixth or seventh, and are directed 
upward and outward. In the articulated skeleton there is a deep 
costo-spinal groove on either side. The zygapophyses are largest 
and stoutest in the posterior cervical region, decreasing gradually in 
size, and becoming obsolete at the base of the tail. Throughout the 
dorsal region they are but slightly cupped, and are directed dorsad 
and ventrad, at only a slight angle from the median plane. There 
are no indications whatever in any region of a zygosphene. The 
centra throughout this region were more or less crushed in the 
specimen, but seem to be very uniform in character. Their size is 
but very little different from that of the posterior cervicals, their 
length no greater; the venous foramina on the ventral side become 
gradually more remote from each other. 

Some of the dorsal ribs were so badly Aeeiiposed that they could 
not be recovered from the matrix; others were so intermingled with 
other bones that they could not be removed entire. The larger part, 
however, have been recovered and restored nearly to their living 
condition. The anterior long ribs are flattened, with an expanded 
head, only moderately curved and with the distal extremity only a 
little attenuated, the cartilaginous continuation evidently of some 
y". SBaur (Anatom. Anzeiger ix, No. 4, 1893, p. 120) would restrict this term to the process bearing 
the head of the rib in the Stapedifera. 


+Seeley has proposed to call these vertebra in which the rib is ascending from the centrum, 
pectorals. 


Oe a aes 


Apr. 1903. NoRTH AMERICAN PLESIOSAURS—WILLISTON. 39 


length. The posterior ribs are short, less flattened, with a less 
expanded head and with a pointed distal extremity. From the 
position of the diapophyses anteriorly, it is quite evident that the ribs 
were directed much more outwardly than downwardly. In the 
restored skeleton, the transition from the long to the short ribs has 
been made gradual, and two or three on each side have been 
modeled here. (See Pl. XI.) 

About fifteen ventra/ ribs were preserved; others have undoubtedly 
been lost. Only one is symmetrical; it is about thirty centimeters in 
length and is thickest near its middle, tapering to a point on each 
~ side, and has a moderate curvature. The others preserved measure 
from twelve to sixteen centimeters, and have a thickness near their 
middle of about ten millimeters. They are gently curved, irregularly 
prismoidal in section, and taper to a point at each extremity. Because 
of their number and the scattered positions in which they were found, 
it has not been possible to arrange them in the mounted skeleton with 
any degree of precision. In the known European specimens they 
form a double series of three, with a larger symmetrical median one. 
Abdominal ribs are known only in the crocodilia, rhyncocephalia 
pterosaurs, ichthyosaurs, dinosaurs and plesiosaurs. 

The caudal vertebre were found at some little distance from the 
remainder of the skeleton, and for the most part had been collected 
separately by Mr. Sternberg. The processes, as elsewhere in the 
column, had been separated, and were, many of them, found variously 
intermixed with the other bones. Both the centra and the processes, 
however, were in excellent condition, as were those of the neck, in 
marked contrast to the dorsal vertebrae. The last twelve taper so 
uniformly that it is quite certain they all belonged together, and that 
no intervening ones were missing. This series has a diameter of 
forty millimeters at the beginning and only twelve at the extremity, 
with lengths respectively of twenty-five and twelve millimeters. The 
greatest decrease in size occurs in the last five or six of the series. 
These distal five or six have the shortening much more pronounced 
on the dorsal than on the ventral side, indicating a well-marked 
upward curvature of the extremity of the tail. Because of the rapid 
change in the characters of these vertebre there has been no difficulty 
of associating the processes with their respective vertebre. The 
spines in the early ones of the series slope at a moderate angle back- 
- ward, the obliquity being greatest in the twelfth from the end. In 
the last six, the spines are much shorter and stand nearly vertically, 
or even with an anterior slope. The diameter of the last centrum 
preserved indicates the presence of two, or perhaps three smaller 


40 FieLp CoLtumBiAN MusEuM—GEo toey, VoL. II. 


ones forming the extreme tip of the tail; these must have been mere 
nodules of bone, without processes. (See Pl. X.) 

Several other vertebre are assigned to the caudal series, chiefly 
on the evidence of the venous foramina on the ventral side of the 
centra, though they have no facets for the chevrons. Between these | 
and the continuous series, four vertebre have been intercalated; the 
number may be too great; possibly not enough. That some were 
missing is quite certain, since the change in the direction of the spine 
is too abrupt in the ones preserved. Because the tail as restored 
seems to be of about the length of some other known forms, I am 
inclined to believe that the number of the caudal vertebre, all told, 
_ did not exceed twenty-five. All those preserved, except the anterior 
ones, show a nearly circular and somewhat cupped surface on each 
side for the attachment of the hemapophyses. The separate branches 
are directed downward, outward and backward. They are somewhat 
flattened and expanded distally, except the distal ones, which are 
more rod-like. The diapophyses or ribs of the connected series 
spring from near the middle of the centra dorso-ventrally, and are 
directed outward horizontally, the most posterior ones also slightly 
forward. They have a somewhat expanded extremity, with a cartilag- 
inous margin. At the beginning of the series they arise near the 
middle of the centra antero-posteriorly, but gradually approach the 
anterior margin. They terminate as free ribs on the seventh before 
the end, that is on the ninth or tenth before the extreme tip of the 
the tail. The sixth has a small exogenous tubercle to represent the 
process. None of the caudal vertebra, save at the immediate base, 
have functional zygapophyses, and the tail was evidently capable of 
considerable lateral and vertical movements. There are no indications 
whatever of a terminal fin, unless the upward curvature of the tip of 
the tail suggests such an appendage. Its use, however, could not 
have been great, since the evident shortness of the tail, and its inter- 
ference with the hind limbs would have deprived it of much service 
as a propelling organ. 


PecToRAL GirpLeE.—The scapu/a is of the usual triradiate shape. 
The coracoid or glenoid ramus is short and rather stout, some- 
what expanded at the extremity, with the two articular facets 
meeting in an obtuse angle, the larger, oval one for the glenoid 
articulation; the smaller, triangular one for union with the cora- 
coid. The ‘dorsal ramus is narrowest, is rather stout, thickened 
on the posterior and thinned on the anterior border; it termi- 
nates in a flattened surface for attachment of a suprascapu- 


i a (2 fic ‘ = are kot E : sia a ie a atin u 
NS eae ee Pe Pern. Bee ey eee ee ee ee ee Re, ee a ee ee ee eee ee oP ee ee Ue TO, at 


-Apr.1903. NortH AMERICAN PLESIOSAURS—WILLISTON. 41 


lar cartilage. The ventral or clavicular (proscapular) extremity 
is broad and thin and deeply concave on its visceral surface. 
Its inner border is rounded for the most part and thin, except 


Fic. 6, 


Part of right scapula of Plesiosaurus mudgei Cragin, external (left,and internal (right) views.” 


on the anterior part, where it is moderately thickened, as though for 
cartilage. The posterior and inner border is quite thin throughout 
and evenly concave, forming the outer anterior border of the scapulo- 
coracoidal foramen. The anterior border is sinuous and thinned, 
having a knife-like edge throughout its whole extent. The exterior 
border, between the glenoid and suprascapular extremities, is deeply 
concave, with the mar- 
gin thickened and 
convex. The ventral 
surface of the bones 
forms two nearly flat 
planes, meeting in a 
straight, prominent 
ridge, which extends 
from the ventral side 
of the anterior border 
_ of the glenoid surface 
to the anterior angle 
of the ventral ramus. 
The two surfaces meet Ventral extremity of scapula of Plesiosaurus gulo Cope (type 
in a very Obtuse _ specimen), one-half natural size. 

angle. The visceral 

surface is, for the most part, concave. On the ventral ramus this 
concavity is marked, receiving the clavicle on its anterior part. 
There is a sutural roughening continued along the anterior border 


Fic. 7. 


. 


42 FIELD CoLuMBIAN MusrtumM—GEo Locy, Vot. II. 


to the base of the dorsal ramus, throughout the whole extent of the 
concave portion of the border. The bone differs from the scapula 
of Murenosaurus* in the less expanded ventral ramus,which is sepa- 
rated from its mate by the clavicle and episternum. From the Crvf/o- 


clidus} scapula it differs in having a more slender and elongate dorsal~ 


ramus, and in the non-expansion of the ventral ramus. From a 
scapula of P/. mudgei Crag. from the Lower Cretaceous in the 
University of Kansas Museum, it differs in its much less slender 
coracoidal and dorsal rami. The bone is also much more slender 
than in Peloneustes. (See Pl. XII.) 

The coracotd is a very large and broad plate, with a slender, 
blade-like epicoracoid projection. Its glenoid portion is massive, 
with a smaller humeral articular surface, and a larger scapular facet, 


meeting each other in a very obtuse angle. The external border is | 


thickened and concave, produced into a considerable projection at 
the posterior angle. Just before its termination there are several 
tooth-like projections of small size, evidently for muscular attach- 
ment. The posterior margin is thin, with rounded angles anda slight 
concavity between them. Opposite the glenoid articulation the bone 


is massive, meeting its fellow in a thickened bar with an oblique | 


sutural surface. Immediately posterior to this interglenoid thicken- 
ing, the bone on the mesial side is very thin, and in the anterior part 
of this thinned portion, near the middle line, there are two large, 
well-defined, round foramina that have never before been described 
in the coracoid, though perhaps indicated in the description of 7Z77n- 
acromerum. The clavicular or epicoracoid process in front is long 
and thin, with nearly parallel sides, the anterior end slightly expanded 
and its margin with a cartilaginous border. The sutural surface for 
the clavicle extends back on the upper surface to nearly midway of 
the process. The coraco-scapular foramen is elongate in shape and 
is bounded entirely by the two bones, save for a short distance at the 
front inner part where the clavicle completes the margin. The cora- 
coid has the posterior outer angle more produced than in: either 
Cryptoclidus, Peloneustes or Murenosaurus, and the clavicular process 
is longer and better developed than has been described in any form, 
except perhaps in 7rinacromerum. 

The clavicle is a thin, concave, irregularly triangular or triradi- 
ate bone, and is well developed. It lies upon the ventral plate of the 
scapula and the epicoracoid process of the coracoid, and above the 
squamous margin of the episternum, a remarkable position for a 


*Andrews, Ann. Mag. Nat. His. xv, 43. 
yAndrews, Ann. Mag. Nat. Hist. xv, 355. 


rear 
“ye ae . 


ee ee oe 


ee ee ee ee eee ee ee. ee ee ae 


* 


Apr. 1903. -NorTH AMERICAN PLESIOSAURS—WILLISTON. 43 


membrane bone to attain on the visceral side of all three cartilage 
bones. The anterior border is gently thickened, somewhat sinuous 
' in outline, and is free for a part of its extent. The other borders are 


ok, 


Fic. 8. 


Diagram of pectoral girdle of Dolichorhynchops osborni, {rom above; the outlines of con- 
-cealed parts are indicated by dotted lines. /c., episternum (interclavicle); c/., clavicle; sc., scap- 
ula; co., coracoid. 


thin, for the most part squamous, and nowhere free, save for a short 
distance at the anterior end of the coraco-scapular foramen, and the 
posterior part of the interclavicular foramen. The two bones meet 


44 Fietp CoLumBian MusteumM—GeEo.oey, VoL. II. 


in a median symphysis for a short distance back of this interclavic- 
ular foramen. The under or convex surface appears only for a small 
space between the ends of the scapule, epicoracoid processes and the 
episternum. Its outer extremity extends into a slender process, 
broken away in the specimen figured, which reaches along the front 
margin of the ventral ramus of the scapula to the base of the dorsal 
ramus. (See Pl. XIII.) 
The clavicle seems to be the most variable bone in the skeleton ; 
I know of no form in which it is better developed. In Cryptoclidus it is. 
a small, triangular bone, meeting its mate in the middle line, according 
to Andrews, the episternum being absent. In Plestosaurus mudget 
Cragin (see Pl. XXVII), the clavicle appears to have been smaller 
and more triangular than in the present species. It is generally 
assumed that this bone is the real clavicle by Seeley, Andrews, Fiir- 
bringer and others, and one may, with Andrews, explain its position 
in relation to the ventral ramus of the scapula by the peculiar method 
of ossification of that bone. But, can its visceral relations to the 
coracoid and episternum be explained as easily? It is true that many 
authors call the median, un- 
paired piece the interclavi- 
cle, a membrane bone, and, 
if this origin is accepted, its 
position in relation to. the 
clavicle is not remarkable. 
But I am inclined, with Geg- 
enbaur and Fiirbringer, to 
believe that this central. piece 
is really the episternum, a 
cartilage bone. Andrews 
described the clavicle in some* 
forms as showing a sutural 
tendency with the scapula, 
and in some forms, as £/as- 
mosaurus, it seems to become 
entirely fused with that bone, 
or if not, has disappeared 
entirely. 
A Fig. 9. je The episternum (inter- 
Miedtie drvei soli daa Meena anonymum Nill. clavicle) is a small, symmet-. 
rical bone deeply emargi- 
nate in front and behind. The thin squamous margin on each 
side underlaps the clavicle. These squamous borders seem to have 


Apr. 1903. Norra AMERICAN PLEs!iosauRS —WILLISTON. 45 


been covered with cartilage below, leaving a free, convex, ventral 
surface, elongate oval in shape, including the emarginations, limited 
by a distinct ridge or angle. The striation of this thinned margin 
points to a covering of cartilage. The anterior emargination of the 
bone is narrow and deep, while the posterior one is broader and even 
deeper. It differs markedly from the corresponding bone of P/. mudgei 
(see Pl. XXVII), in its less broad and deep emarginations. An 
episternum which I provisionally refer to the species 77. anony- 
num, herewith figured, resembles that of D. osborni more closely. In 
all three, perhaps belonging to distinct genera, it will be seen that 


Fig. 10, 


1, Episternum and clavicles of Muraenosaurus ; 2, 3, the same of Plesiosaurus, from above and 
below. After Seeley. 


~ * »* 2 : te, Peg Pe 
¥ - = 
: sd 


46 Fietp Co_tumpian MustEumM—GEo toey, VoL. II. 


the emargination behind represents a distinct foramen in the com- 
pleted girdle—the interclavicular foramen, of which the only mention 
hitherto that I can find is hy Seeley (Proc. Roy. Soc. Lond. li, p- 140), 
whose figures I reproduce here. 

In Pl. XV is shown the articulated pectoral girdle from below, 
and in Pl. XIV, the same is shown in front view. As a whole, 
the girdle forms a rather deep trough, with the dorsal rami of the 
scapula directed upward and somewhat outward. Its exact position 
in relation to the ribs is dificult to state, but I do not think that the 
position given in the restoration can be far wrong. The slight 


‘ ; Fig. 11. 


Scapulo-clavicular girdle of Plesiosaurus mudgei from above; the missing parts restored in 
dotted lines. /c., episternum; c¢/., clavicle; sc., scapula; co., epicoracoid process. 


degree of curvature of the ribs in the pectoral region must have left a 
rather angular margin to the thorax on either side, filled in, in part at 
least, by the cartilaginous continuation of the thoracic ribs, which 
the preserved ends plainly show were present. The upper surface of 
the girdle was not hollowed much, if any, longitudinally, so that the 
base of the neck must have been in life quite deep. 

An examination of the under surface of the girdle, as shown in 
Pl..XV, furnishes, I think, convincing proof that the space between 
the scapule, epicoracoid process and the elliptical lines on the ven- 
tral surface of the episternum was filled in in life by cartilage, join- 
ing the coracoid and scapula and covering the squamous portion of 
the episternum, but leaving the interclavicular foramen free. Ossifi- 


/ 


. 
~ 


Apr. 1903. NortuH AMERICAN PLEsIOSaURS —WILLISTON. 47 


cation of this cartilage evidently’ occurs in some forms, uniting the 
whole into a single ventral plate, which is said to have a sutural con- 
nection with the epicoracoid processes, forming what Seeley calls the 
Elasmosaurian type of girdle. Seeley suggests that this cartilage 
may represent the precoracoid: ‘‘In all Plesiosaurs, on the other 
hand, the precoracoid, if developed, remains cartilaginous; but I 
infer that a cartilage always extended from the anterior margin of the 
coracoid to the anterior extremity of the scapula, and, by ossification 
of such cartilage, the Plesiosaurian shoulder girdle would become 
Elasmosaurian.’”’* 

This precoracoid nature of the cartilage is contested by Koken: 
‘«The view that the bone considered to be the scapula in the Plesio- 
saurs also includes the precoracoid is supported neither by compar- 
ison nor observation. In no reptile has there been shown to bea 
union of the scapula with the precoracoid more intimate than its 
union with the coracoid, and its fusion with the scapula without 
union with the coracoid would be remarkable. I agree quite with 


- Baur, who considers the forked bone of the turtles to be the scapula 


only, its two branches being homologous with those of the plesiosau- 
rian scapula. Seeley believes that the precoracoid was cartilaginous, 
connecting the front end of the coracoid with the anterior end of the 
scapula, and that this became ossified in the Elasmosaurians in such 
a way that it was separated from the coracoid by suture, but was 
fused with the scapula. That is, it is the precoracoids and not the 
scapule which meet in the middle line. It seems to me that this 
would be the method of extension and ossification of the scapule. 
Why, then, should we call in the aid of a cartilaginous precoracoid as 
an unknown quantity, which later becomes indistinguishably fused 
with the scapula?”’} 

The precoracoid arises from a distinct ossificatory center, when 
ossified. Is it reasonable to suppose, then, if this is a distinct ele- 
ment, that any such mode of extension of the scapula as Andrews has 
shown to be the case in Cryftoclidus oxoniensist would occur if there 
was really a union of scapula and precoracoid? He shows clearly 
that the scapula increases in length peripherally, and not by the addi- 
tion of an ossified cartilage. If it arose from a distinct center, as it 
must, one would certainly expect to find it in a separated condition 
in the young animal, but this was not the case in the ones that 
Andrews examined. Furthermore, in what possible way could a carti- 

*Proc. Roy. Soc. Lond. li, p. 138, 1892. 


tKoken, Zeitschr. Deutschen Geol. Gesellsch. 1893, xlv, 346. f 
tAnn. Mag. Nat. Hist. 1893. 


48 FieLp CoLumpian MuseumM—GeEo toey, VoL. II. 


lage bone like the precoracoid get entirely on the outside and seal in 
a membrane or dermal bone? I| would sooner believe that the 
so-called clavicles are really precoracoids, and for this belief their 
position on the visceral side of all three cartilage bones, the scapula, 
episternum and coracoid, would lend some support. In no case, how- 
ever, can | believe it probable that this cartilage represents the pre- 
coracoid. 

The same argument will apply in its entirety to the assumption 
that the ventral ramus of the scapula is in reality the precoracoid. 
In no specimen has it ever been found as a distinct ossification. It 
grows peripherally, enclosing the clavicles on their outer side. The 
elongated clavicles unite by suture with the scapula in the Notho- 
sauria without the intervention of any precoracoid process. By the 
reduction of the clavicles and the extension of the acromial process in 
these animals we would get the Plesiosaurian girdle. Is it necessary 
to insert a distinct ossificatory element in this development? 

It may be added that Koken believes the precoracoid to be fused 
with the coracoid. 

I cannot, therefore, believe that the precoracoid is represented 
. by any ossification in the plesiosaurian clavicular girdle. Nor do I 
believe there is any genetic relationship between the ventral ramus 
of the Plesiosaurs and that of the Chelonian scapula. If there is, is 
it not strange that in the one case the branch should lie ventrad to 


the clavicle and in the other dorsad? I am well aware that in thus . 


concurring in the views held by Seeley, Andrews, Koken, Baur and 
others, there are pertinent arguments on the other side given by 
Hulke, and especially Fiirbringer.* 


Petvic GiroLe.—The fwd7s varies but little from the usual form. 
It is a broad, flattened plate of bone, thinned throughout, except at 
the symphysial and acetabular articulations. It is, in general, quad- 
rilateral in shape, with the anterior inner angle broadly rounded, and 
the acetabular angle truncated. The posterior and outer borders are 
both markedly concave, and of about equal length. “The anterior 
border is more nearly straight and irregular. The inner border is 
thickened on the posterior third or half, gradually becoming thinner 
anteriorly. The obliquely truncated sutural surface is much rough- 
ened. ‘The two bones, when united, must have made an angle with 
each other of about one hundred and twenty-five degrees. I do not 
think that there was much cartilage between the two, or that it 
extended back to the ischial symphysis, though it may. Anteriorly 


Jena. Zeitschr. 1900, p. 332. 


i og t 


Apr.1903. NortH AMERICAN PLEsIOSAURS—WILLISTON. 49 


4 


the cartilage continued to the rounded outer anterior angle, where 
the bone is a little more thickened. The acetabular surface is much 
the larger of the articulating facets. It meets the smaller and rough- 
ened facet for the ischium in a very obtuse angle. The bone is more 
thickened on the outer and posterior parts, that is, near the non- 
cartilaginous border, than elsewhere. (See Pl. XVI.) 


pu 


Fig. 12. 


Diagram of pelvic girdle of Dolichorhynchops osborni, visceral surface, Pu., pubis; ist, ischium; 
#., ilium. e 


The éschium is more elongate and proportionally larger than is 
usual among plesiosaurs, though of the usual hatchet shape. It has 
three non-sutural articular surfaces—the larger middle one, looking 
directly outward in the articulated ischium; a smaller posterior one, 


50 Fretp Cotumpian Museum—Geotocy, Vot. II. 


looking upward; and a small one looking forward and a little down- 
ward for the pubis. The anterior border is concave, and the portion 
adjacent to this border is the thickest of the bone. The symphysial 
border is thickened on the anterior third, gradually thinning posteriorly. 
This border is obliquely truncated, as in the pubis, anteriorly; poste- 
riorly the cartilaginous border, moderately thin, is continued around 
the inner angle to the outer one, where it meets the free outer border 
abruptly. The outer border is gently concave in its whole extent, 
and only a little thicker than the inner portion of the bone. It ends 
in aright angle. (Pl. XVII.) 

The ¢déum is a small, rod-like bone, moderately expanded at its 
ischial extremity. Of the two articulating extremities, that for the 
ischium is much larger than the one for the acetabulum. In the 
middle of the bone, a cross-section is roundly oval. The upper 
extremity has a small, flattened, parallelogrammatic surface, which, 
in the articulated pelvis, looks inward, slightly backward, and 
perhaps a little downward. The bone when articulated was directed 
backward at an angle of about thirty degrees, and inward ‘perhaps a 
little more. There is very little evidence of articulation with the 
sacral ribs. The union must have been weak and slight. 

The pelvis, as a whole, was troughlike, as was the pectoral girdle. 
The two bones meet at a considerable angle, and it is also certain 
that there was a large angle between the ischium and pubis, so that, — 
with the ischial symphysis nearly horizontal, the pubes were directed 
at a considerable angle downward. This position, indeed, is necessary, 
since otherwise there would have been a strongly upward turn of the 
abdominal contour immediately behind the coracoids, and the ischia 
and pubes will articulate in this position only in this specimen. 


Front Limes.—The paddle-bones of the specimen were all com- 
pletely intermingled and displaced, so that none could be referred to 
its proper limb from the position they were in. 

Apparently nearly all were preserved, though some of them were 
distorted and crushed. The labor of assorting and correctly locating 
these parts was very great, especially the phalanges; indeed, of the 
latter there is little assurance that the final collocation in many cases 
is correct. Aside from the femora and humeri, the only distinction 
that could be made between the bones of the front and hind limbs 
was in the size, always slightly smaller in the hind than in the fore 
limb. By thus assorting into pairs and assigning the smaller pair to 
the hind limb it was certain that the bones of the epipodial and meso- 
vodial regions were correctly placed. The labor was much lightened 


eee 


Apr. 1903. NortTH AMERICAN PLESIOSAURS—WILLISTON. 5! 


by the aid of a nearly complete paddle of another species, described 
further on. This paddle was less compressed and distorted, and I 
have therefore reserved it for a more full description of the parts and 
discussion of the functions. 

The humerus of Dolichorhynchops has the head only moderately 
convex, with its margins rather sharply limited, its greater convexity, 
as usual, on the radial side; its general surface looks mesad and 
ventrad at an angle of about forty-five degrees. Its cartilaginous 
surface is continuous with that of the tuberosity, which has a large, 
flat surface, directed dorsad and mesad at an angle of about forty-five 
degrees. The grooves separating the surface from the head are 
broad and shallow, that of the ulnar side the broader. The anterior 
border of the bone is concave on the proximal part, gently convex at 
the middle and shallowly concave on the distal part. The posterior 
border is nearly straight on the shaft, deeply concave distally. The 
distal anterior angle is rounded in both specimens. On the distal 
border two facets are apparent, for the radius and ulna; the rest of 
this border presents no clear indications of articulations. The 
pectoral rugosity is strongly roughened, and produced into a broad, 
low tubercle; the roughening, moreover, is continued obliquely nearly 
to the other rugosities on the sides. It is situated nearer the head 
than in Polycoty/us. The ulnar rugosity forms a deep pit above the 
middle of the bone, while the radial rugosity is opposite it and much 
nearer the head of the bone than in Podycoty/us. 

Three bones were certainly located in the fore-arm, and a fourth 
one seems to be represented by a pair of small nodules. The free, 
emarginate border between the radius and ulna is less apparent than 
it is in Polycoty/us. The relations of all the smaller bones seem to 
be quite as they are in Po/ycoty/us, and the reader is referred to the 
figures of the two paddles for comparison, in connection with the 
description of that of Polycotylus. ' 


Hino Limss.—The femur shows the usual plesiosaurian differences 
from the humerus, in its greater slenderness, slightly greater length, 
more slender shaft and less dilated distal extremity. The anterior 
border, as seen in the figure, is nearly uniformly concave, terminating 
in a more pronounced angle than in the humerus. The posterior 
border is, also, concave throughout to the greatest expansion, which 
occurs more proximally than in the humerus, and in a rather better 
marked angle. The rugosities of the under side and margins are as 
in the humerus, though scarcely as well marked. Whether the bones 
of the leg and ankle have been correctly located, rather than in the 


52 Fietp CoLumBiAN MusruM—GeEo.ocy, VoL. II. 


fore limb, is impossible to say—the only differences that could be 
detected are the rather lighter weight or greater slenderness of those 
located.here, Their relations to each other are precisely those of the 
fore limb. It seems probable that the fourth bone on the posterior 
side of the first row, articulating with the femur, was wanting in life, 
or at least wag very small—none were preserved. The fore and hind 
limbs, as restored, are of the same length. All four paddles were 
restored as completely as those shown in the figures. | : 


CIMOLIASAURUS SNOWII. 


Skutt.—The skull of this species was briefly described by me in 
the Transactions of the Kansas Academy of Science:for 1890, to which 
some additional observations were made by Cope in the Proceedings 
of the, American Philosophical Society for 1894, p. 109. I give here 
a more complete comparative description, in the light of the infor- 
mation furnished by other known forms, especially Dolichorhynchops. 


FiG.13. 


Skull of Cimoliasaurus snowii Will. Pm. premaxilla; e7., external naris; wx., maxilla; Af, 
prefrontal; Zof., postfronto orbital; 7., jugal; sg., squamosal; fa., parietal; so., supraoccipital; ¢o., 
exoccipital; g., quadrate; g7. quadratojugal; d@, dentary; swr., surangular; azg., angular. 


The parietals form a steep, roof-like covering, ascending into a 
thin, sharp, sagittal crest, extending through nearly their whole 
length, from the attachment of the squamosals posteriorly as far for- 
ward as the posterior part of the orbit, This crest, throughout most 
of its extent, forms a thin, vertical plate, with nearly parallel sides 


eS Ss <=, ee eee 


ApR. 1903. NortH AMERICAN PLESIOSAURS—WILLISTON. 53 


for about two inches, its thickness on the margin varying from two 
to four millimeters. Posteriorly they expand into a thickened, trian- 
gular process on each side, projected downward and backward over 
the supraoccipitals for union with the squamosals. Extending the 
whole length of the crest is a well-marked suture. Near the anterior 
extremity of the crest is the parietal foramen, which has been closed 
by compression. 

The postorbital appears as a narrow bar directed outward and 
downward. Its union with the supraorbital above and the squamosal 
below is shown in the figure. The bone is triangular in shape, as 
seen externally, the suture for the jugal extending back horizontally, 
and is then turned upward at right angles to meet the free margin of 
the arch. : 

The suture separating the jwga/ from the squamosal begins at 
the angle of the postorbital suture and runs obliquely downward and 
backward to meet the lower border of the arch about fifty millimeters 
back of the teeth. The suture is a jagged one, but its existence as 
described and figured is beyond doubt. Professor Cope figured it 
much further back on the arch, but his supposed suture is very plainly 
a fracture. The bone unites below with the maxilla by a long, nearly 
horizontal suture, that begins in an angle a little back of the middle 
of the orbit and joins the alveolar margin near the last tooth. The 
anterior part of the suture is nearly at right angles to the remainder, 
joining the orbital margin back of the middle of the orbit. 

The sgwamosal, or squamoso-prosquamosal, is a large, triradiate 
bone joining the jugal and the postorbital anteriorly, the parietal 
above, the quadrate and quadratojugal below. Cope has figured the 


- upper branch as a distinct bone under the name of supramastoid. 


This was an error, as has already been stated. At the anterior infe- 
rior part of the quadrate there is a distinct suture, as has been 
figured, corresponding to the suture described as existing here in the 
specimen of Dolichorhynchops. In the figures given of C. snowitt, it 
was supposed that the quadratojugal was a small element. It now 
seems probable that its relations to the squamosal are like those of 
Dolichorhynchops; at least there is an indication that the real suture is 
continued upward and forward for some distance. The union of the 
squamosal and quadrate is very much as it is in Dolichorhynchops. 

The guadrate does not seem to differ from that described in Dod- 
chorhynchops. 

The premaxillary is very large and massive. Its dentigerous por- 
tion is broad and thick, with numerous pit-like depressions. It con- 
tains six very large and powerful teeth on each side, the maxillary 


54 Fietp CoLtumpian Museum—Geotocy, Vot. II. 


suture beginning just back of the sixth tooth. The distinguishing 
suture turns upward and backward to meet the anterior end of the 
external nares in front of the orbit. Above this, for a short distance, 
the bone is so crushed that the suture is not determinable with cer- 
tainty, but the upper end is evident, nearly above the middle of the 
orbit. The suture separating the two premaxille is distinct 
throughout. 


The maxiiia has on each side sockets for twelve or thirteen teeth, 


all, except a few of the anterior ones, much smaller than those of the 
premaxilla, and smaller than those of the mandible in this region. 
From the nares, which are chiefly excavated from this bone, the 
suture turns upward and backward for about twelve millimeters, sep- 
arating the nasals; it then turns downward and backward to join the 
anterior orbital margin, uniting with the prefrontal. The lower 
anterior’ margin of the orbit is thus formed by the maxillary plate, 
which shows a shallow groove. The maxillary plate on the: left is 
smooth and undistorted, the nasal and prefrontal having been sepa- 
rated at their sutures. _ There is no indication whatever of. a separa- 
tion into two elements, nor is there any free lachrymal. Posteriorly 
the maxilla forms a rather broad plate below the orbits, having a 
convex thinned margin continuous with that of the jugal. Back of 
the middle on this margin, the suture for the jugal turns directly 
downward for about twelve millimeters, and then backward in a 
straight line to terminate just beyond the last tooth. 

That element which, in Dolichorhynchops, is described as the 
supraorbital, is a much more massive bone in Cimoliasaurus. It 
unites with the postorbital by a strong suture, behind the middle of 
the orbit above, and is not separated by a deep notch_as in that 
species. The bone arches forward and downward to beyond the 
middle of the anterior part of the orbit, as in Dodlichorhynchops, stand- 
ing out prominently over the orbit and terminates in a strong suture 
by which it is united to the ascending plate of the maxilla, as has 
been described. Its union with the prefrontal or frontal cannot be 
determined in the crushed state of the specimen. Such relations of 
a supraorbital bone with the postorbital, maxilla, nasal, etc., are almost 
inconceivable, but are altogether right for a prefrontal.’ If this be a 
prefrontal, then the same element in Do/ichorhynchops must also be 
the prefrontal, and the so-called postprefrontonasal is in reality the 
frontal, while the anterior prolongation from the parietal.is in reality 
a process from that bone, separating the frontals, a most remarkable 
arrangement for any vertebrate skull. I am forced to believe, how- 
ever, that such is really the explanation of these bones. 


aa 
oi 
4 

— 
S 


i ln all lel ee 


Apr. 1903. NortH AMERICAN PLESIOSAURS— WILLISTON. 55 


The supraoccipitals are visible from the side behind and are not 
covered over by the wing-like expansions of the parietals, as in Do/i- 
chorhynchops. They are paired and separated throughout, as in that 
genus. Below they unite with the exoccipital, and include a part of 
the semicircular canals. Above and in front they join the parietals 
at their posterior margin and not under the roof. The exoccipitals_ 
are also visible. The paroccipital process is slender, its posterior 
margin thin, joining the supraoccipital in an angle without the small 
excavation which is seen in Do/ichorhynchops at this place. 

* Lying within the orbit are thirteen thin, bony sec/erotic plates, the 
largest about twenty millimeters in ‘diameter, with somewhat crenu- 
lated margins. The larger number are lying in position, imbricated 
with each other. 

There are sockets in the mandibles for nineteen or twenty teeth 
on each side. Those in the upper jaws seem to be the same in num- 
ber, though the small posterior ones are so covered by the inferior 
teeth that the number cannot be positively determined. The largest 
teeth implanted in the upper jaw are those of the premaxilla; back 
of these there is but a single large tooth, situated just in front of the 
orbit. The largest teeth of the mandible are the ones corresponding 
to those of the premaxilla; the posterior ones, however, are much 
larger than the corresponding ones. of the upper jaw. The anterior 
teeth, especially, are elongate, conical and lightly recurved. All are 
sharply pointed, with the crown; within a half or three-fourths of an 
inch of the socket, finely striated. The largest is that of the pre- 


‘maxilla just in front of-the maxillary suture, which measures fifty- 


three: millimeters in length by thirteen in width at the base of the | 
crown. The first tooth in the mandible is fully as long, though a 
little more slender. 

The fterygoids are so crowded in between the mandibles and 
maxillz that only a portion of them is visible. The posterior part 
joins the quadrate by a stout plate, as in Dolichorhynchops. By the 
sides of the sphenoids the plates are broad and massive, with a 
thinned outer crenulated margin. The ecfopftervgoid unites with the 
jugal and maxilla. Evidently there are elongated interpterygoid 
vacuities, as in Dolichorhynchops. 

The mandible, from the tip of the symphysis to the hind extremity, 
measures ‘480 millimeters, of which the teeth occupy 320. Its least 
width, near the middle, is 40 millimeters; its greatest width, just back 
-of the teeth at the coronary eminence, is 75 millimeters. The length 
of the symphysis is 65 millimeters. The two sides are firmly codssified, 
traces of the suture being visible in the posterior part only. The 


56 FieLp CoLumpian MusrumM—GEo.ocy, Vot. II. 
sutures separating the angular, surangular and dentary are shown in 
the figure. 

CERVICAL VERTEBRA.—There were twenty-eight cervical vertebrz 
in’ a continuous series preserved, the last five or six, owing to 
exposure, in a less perfect condition; the others complete or nearly 
so. Traces of the sutures uniting the neural arches with the centra 
can be observed in the third and fourth vertebra only. The atlas and 
axis are so wedged in the compressed occipital region that the former 
bone can not be distinguished, and the latter is visible in part only. 
The third vertebre, herewith figured, differs from the following ones 
in the greater obliquity of the spine, in thé more oblique anterior 
face of the centrum, in the presence of a conspicuous carina below in 
front, and in the simple, pointed shape of the single-headed rib. The 
fourth vertebre has the neural process less oblique and broader, the 
carina in the middle of the concavity of the under surface not visible 
from the side; the rib is broad and of nearly equal width throughout. 
In the sixth vertebrze and beyond the neural process is broader and 
nearly vertical; the ribs are broad, with more marked anterior and 
posterior prolongations distally. The spines increase in width through- 
out the series, but are only a little longer posteriorly. The posterior 
centrum is more than three times the length of the anterior ones and 
the diameter’ posteriorly is more than twice that anteriorly. The ribs 
of the posterior vertebre are but little longer, though much wider, 
than those of the anterior vertebre. The following measurements 
will exhibit these’ differences in size more exactly: 


NUMBER OF VERTEBRA. 3 4 6 9 I4 20 27 
Length of centram 3.) <.)5" 32907 7 23 30 48 53 63. | 78 | ere) 
Height of centrum . . ... 25 27 42 44 50 60 | 68 
Height of spine above floor . | 

of neural canal . 2... 55 46 47 47 50 | 62 , 
Width of Spine 2. soo ee Ree hee ee 36. | 40: ae 8S be. 
Length of rib. 8 af. Paes a8 Re, Cater 


Widihobrib 26. oo Pa eta) Oe ag 56 oes 


q That = a Riga ee 
Breen: 


Apr. 1903. NORTH AMERICAN PLESIOSAURS—WILLISTON, 57 


BRACHAUCHENIUS LUCASI, GEN. ET SP. NOV. 


The specimen upon which this genus and species are based is 
one of much interest, not only because of its excellent preservation 
and preparation, but also because of the new features which it 
presents. It consists of the skull, neck, and larger part of the dorsal 


‘column, all lying together in their natural relationships, and all with 


the ventral surface exposed, in the prepared specimen. The specimen 
was collected some years ago near Delphos, in Ottawa County, Kan- 
sas. Its horizon is the Benton Cretaceous. It is now preserved in a 
wall-case in the National Museum. I desire to express my hearty 
thanks to the authorities of the National Museum for permission to 
study and describe the specimen, and especially to Mr. F. A. Lucas 
for much kind assistance. It gives me great pleasure to honor, in 
the specific name, one who has done much valuable work in American 
paleontology. (Pls. XXIV, XXV.) 


Sxutt.—The palatal surface of the skull lies exposed, with the 
mandibles in position. There has been but little distortion or dis- 
placement, the mandibles being slightly depressed and pushed to the 
left. The limestone matrix'has been carefully removed from most 
parts, leaving the bones entirely clean. The sutures are entirely 
clear, and there are but few adventitious fractures to obscure the 
relations of the parts. It is certain that additional excavation will 
reveal further characters of importance, but not many, unless the 
specimen be entirely removed from the matrix. The specimen as: 
now mounted in the wall slab makes a very interesting and instructive 
display, but I believe that some day it will be advisable to remove it 
entirely from its limestone bed and mount it after the manner of a 
recent skeleton. It was fortunate, however, that this was not done 
before a careful examination had been made of the natural relations 
of the bones, as it would have been difficult to believe that the neck 
comprised but thirteen vertebra, had not the matrix conclusively 
demonstrated the fact. It is the shortest-necked plesiosaur known, 
differing in this respect not greatly from the short-necked aquatic 
saurians of other orders. 

The fferygoids extend far back to unite with the lower end of: the 
quadrates, apparently quite as usual in the plesiosaurs, though the 
precise place of junction is obscured by the mandibles; the process 


58 FieLp CoL_umBiAN Mustum—GeEo ocy, Vou. II. 


is slender. The two bones meet in a median suture on the under 
side of the sphenoid, their posterior border forming a wide and deep 
concavity. The outer margin of the bones converge from the quad- 
rates as far forward as the posterior end of the interpterygoid vacui- 
ties, where they curve outward into the posterior border of the ecto- 
pterygoid processes. The under surface is shallowly concave on 
either side back of the vacuitiés, but in the middle there is a rather 
strong, obtuse ridge. A little back of the vacuities, on either side, 
with their origins separated, a narrow and strong ridge arises to 
curve outward and become lost on the under border of the somewhat 
descending ectopterygoid process. In front of the vacuities the two 
bones again meet in a long median suture. The palatal surface here 
occupies a somewhat higher plane than that of the posterior part, and 
is flat throughout. The bones of the two sides gradually narrow in 
width to terminate by an obtuse extremity near the middle of the 
palate. Between the ectopterygoid processes and between the curved 
ridges already described there is a narrow, deep vacuity, with two 
oval, elongated, well-defined foramina or vacuities at the bottom, the 
‘‘palatonares”’ of Owen, the ‘‘posterior palatine vacuities” of 
Andrews, the ‘‘interpterygoid vacuities” of authors. A discus- 
sion of their character will find a place further on. The lateral walls 
of this fossa posteriorly are nearly vertical, but the anterior end of 
the fossa is but little or not at all excavated above the plane of the 
palate here. From the anterior end of the median posterior inter- 
pterygoid suture two sutures diverge, leaving a large angular sloping 
surface exposed which forms the posterior roof of the fossa; the bone 
exposed between the V-shaped sutures is the basisphenoid, and has 
attached to it by suture the so-called parasphenoid bone in front. 
‘Just how the diverging sutures terminate I cannot definitely say. 
They seem to follow the lower angle of the lateral wall of the fossa 
as far forward as the middle of the vacuities and thence return to join 
the parasphenoid suture at the posterior part of the vacuities. If 
this determination is correct, these projections would correspond to 
the basipterygoid processes of the lizards. The ectopterygoid pro- 
cesses ot the pterygoids, the continuation of the curved ridges, have a 
rounded, prominent under border, with a terminal, large, vertical or 
oblique, abutting, mandibular surface. This ridge and its abutting 
surface are very much as they are in P//osaurus, and the whole struc- 
ture here also reminds one of the crocodiles. 

The transverse, transpalatine or ectopterygoid bone is a rather 
small, flattened polygonal bone, whose under surface is continuous 
with that of the palatine and pterygoid in front. It joins the ptery- 


~ Apr. 1903. NorTH AMERICAN PLESIOSAURS—WILLISTON. 59 


goid on the inner side and behind, the posterior suture descending on 
the side of the projecting process of the pterygoid. To what extent 
the bone enters into the abutting surface for the mandible | could not 
determine. Anteriorly the bone joins the palatine by a clearly 
marked suture. Its outer border posteriorly is rounded and seems to 
be free, forming a part of the border of the posterior palatine vacuity, 
but this can not be determined without further excavation of the 
matrix. The outer attachment of the bone (doubtless to the jugal 
and maxilla) cannot be determined. 

The palatines are long flat bones which meet for a considerable 
distance in a median suture in front of the pterygoids, a feature hith- 
erto unknown among the plesiosaurs. In front this median suture 
divaricates to admit the pointed extremities of the vomers. A little 
distance from the interpalatine suture, near its middle, there are, on 
either side, two or three small, round foramina. The outer border 
of the palatines continues the border of the ectopterygoids throughout 
and is continuous, apparently with the lateral border of the vomers. 
How far this apparent border in the specimen represents the real 
border of the bone cannot be determined without additional excava- 
tion of the matrix, here filling in a narrow space between the apparent 
margin and the mandible. It is possible that there may be no free 
border, though I think it probable that there is a smaller or larger 
posterior palatine vacuity on each side posteriorly. It is probable 
that the sides of the bones turn upwards to meet the maxille in the 
way they are figured by Sollas in Plesiosaurus.* 

The posterior pointed extremities of the vomers are seen in the 


middle in front, enclosed between the V-shaped suture of the pala- . 


tines. The suture seems to be visible to the border of the palatine 
and includes no part of a narial opening. The nares hence must be 
situated far forward between the vomers and the maxilla. Unfor- 
tunately this part of the skull has been injured somewhat before 
removal, and the complete structure here cannot be determined. 

The so-called ‘‘ parasphenoid” is different from that element in 


other plesiosaurs. It is a single bone separating the interpterygoid 


vacuities. As seen from below, it is spindle-shaped, narrow in the 
middle, moderately expanded at either extremity. Posteriorly it is. 
joined by a clearly marked suture with the basisphenoid. Anteri- 
orly it joins the two pterygoids in the entrant angles, but does not 
extend much, if any, beyond the angle. The vacuities separated by 
this bone are long and oval, situated at the bottom of the fossa 
already described, between the pterygoids and in front of the basi- 


*Quart. Journ. Geol. Soc. 1881, p. 475, f. 12. 


60 Fietp CoLtumpian MuseumM—GeEo tocy, Vot. II. 


sphenoid. It would seem that there could be no further question as 
to the character of these vacuities—simply fortuitous openings— 
separated by a remarkably persistent, well-ossified parasphenoid, 
invariably found in all plesiosaurs, but never in their nearest allies, 
the turtles and nothosaurs. In most of the plesiosaurs in which the 
palate is known, the openings are situated more nearly upon the 
plane of the palate, and, though somewhat variable in shape, are 
always of moderate or considerable size. In this species, however, 
they are at the bottom of a well-marked, rather deep fossa, with well 
defined lateral walls and a sloping posterior roof. 

These foramina in the plesiosaur skull were first thought to be 
the nares by Owen, who, however, confounded the anterior part of 
the pterygoids with the palatines. ~Huxley, who was also not clear 
about the palatines, suggested that the real internal nares were smaller 
openings situated more anteriorly. Sollas (1. c.) discussed the matter 
more at length and reached the conclusion that the real internal nares 
were situated far in front, between the premaxilla and vomer, with 
the palatines probably entering into the posterior border. Andrews 
has accepted this location of the nares, and has figured and described 
the openings in three genera of the plesiosaurs, always bounded by 
vomer, palatine and maxilla. In Dolichorhynchops osborni, however, 
as seen from the figure and descriptions, these openings can only be 
situated between the vomers and palatines and at some distance 
from the maxilla. In my description I accepted these orifices as the 
true nares, though greatly astonished at their minute size, and 
althoygh they correspond with similar foramina between the vomers, 
in the mosasaurs. 

If we are to seek for the nares in their present specimen else- 
‘where than in the openings I have described it must be far forward, 
perhaps in precisely the position assigned to them by Sollas. In all 
the known forms, with this interpretation, they would be in front of 
the external nostrils, in the present species far in front. What 
possible combination of circumstances would havt caused the recession 
of the external nostrils to a place so close to the orbits without 
affecting the position of the internal openings? I certainly suspect 
that in this species at least the openings between the pterygoids are 
the real internal nares. As to the character of the separating element 
I am forced to the conclusion that Andrews has reached, that it is 


the parasphenoid. If the element in front called the vomers are . 


really those bones, and there could seem to be no doubt that they are, 
there is nothing else left, save possibly the turbinated bones. 


The slender bone in precisely similar position in the ichthyosaurs . 


y ae ae 


| 
: 
; 
; 
] 
4 
: 
: 
4 


Apr. 1903. NortH AMERICAN PLESIOSAURS—WILLISTON. 61 


- is usually called the presphenoid. Such perfect and _ persistent 


ossification of the parasphenoid, scarcely found elsewhere among the 
reptilia, unless it be the snakes, is in any case remarkable. Why 
should it be persistent in separating such persistent foramina, unless 


the openings were of functional importance? One would expect 


that the pterygoids would have united along the whole median 
line, as in the Nothosauria, or that they should have closed up 
in front of the basisphenoid, as ‘in the Chelonia. Sollas objects 
to this posterior position of the nostrils, because there is no ossified 
canal for the air passages, as in the crocodiles; but his specimen, as 


- ours, would call for a canal running in the opposite direction, from 


the posteriorly situated external nares anteriorly to the internal open- 
ings, and, in the present species, this canal would have been eight or 
more inches in length. And why may not the canal have been 
cartilaginous in either case? 


Manoiste.—The mandibles are nearly in place on the under side 
of the skull. They are a little compressed from above downward. 
The symphysis is short, the two jaws meeting in a considerable angle. 
The portion in front of the posterior end of the symphysis has been 
somewhat injured in the specimen, so that the precise: shape and 
length can not be ascertained. The angular extends posteriorly into 
a relatively short process; the expansion below the cotylar cavity 
is rounded. In front of the cavity, the angular extends forward to 
within six inches of the symphysial angle, terminating in a slender, 


‘sharp end. From a little in front of the middle of the ramus it is 


excluded from the inner surface. In front of the cotylar cavity the 
greater width of the outer surface is composed of the surangular. 
Between these two bones, the dentary sends a long, slender process 
backward to within six inches of the cotylar cavity. 


Length of skull to end of mandible. . See é ER, 
Length of skull to condyle . ; ‘ i ; om. 
Width of skull between outer margins of quadpais : ‘ : .28 m. 


VerTEBRZ.—The atlanto-axial complex is thoroughly united, with- 
out indications of sutural division. The axial rib appears to be 
united with the axis only, though it may come in contact with the 
axial intercentrum. The atlas is convex from side to side, without 
indication of a median carina. The other cervical centra, as seen 
from below, are nearly flat, with a slight convexity in the middle, and 
a slight concavity on either side before the sutural surface for the rib. 
This flatness is a natural character and not due to compression. The 
median convexity increases gradually throughout the cervical series. 


62 Fietp Cotumpian MuseumM—GeEo tocy, VoL. II. 


The increase in length of the cervical vertebre is slight, as will be 
seen from the table of measurements. The articular margin of the 
vertebrae, throughout both the cervical and dorsal series, is sharp, 
not rounded for a continuation of the cartilaginous surface, as is so 
often the case among plesiosaurs. The ends, as seen in the third 
vertebra, are distinctly though not deeply concave. The ventral 
vascular foramina, so characteristic of plesiosaur vertebre, appear to 
be wanting throughout the whole series, nor is there the slightest 
indication of a median ridge and lateral grooves. The lower margin 
of ‘the rib articulation approaches the ventral plane in the early 
-cervicals, but ascends somewhat on the sides of the vertebra in the - 
last cervical. 

Twenty-two dorsal vertebre are preserved in natural sequence. 
Because of the decrease in the length of the transverse process in the 
late dorsals, it does not seem probable that more than eight or ten 
presacral vertebre could be missing, making altogether about thirty, 
the usual number of dorsal vertebre. The length of the centra 
increases more rapidly, though gradually, in the early dorsals, and 
then remains constant throughout the remainder of the series. The 
centra are deeply concave below and on the sides, expanding out- 
wardly on the sides above to meet the sutural surface for the arch. 
The surface of the centra is nearly smooth, with but slight indications 
of crenulations before the articular margins. 


Riss.—The ribs throughout are single-headed, and of the usual 
plesiosaurian type, though proportionally short in the thoracic region. 
The axial rib is flattened spatulate at the distal extremity; massive at 
the proximal. The lower surface is nearly flat, the upper surface 
deeply concave, the anterior border gently, the posterior border deeply 
concave. The rib of the third vertebra is more expanded distally, - 
with the distal posterior margin somewhat more produced, and the 
distal border thinned. The fourth rib is more expanded distally, with 
a more pronounced distal expansion, and the distal border seems to 
be thickened for cartilage. The next four or five ribs differ only 
slightly from the preceding ones. The rib of the tenth vertebre is 
more elongated and slender. The attachment to the centrum is 
sessile or nearly so, the head inserted in a shallow pit. In the 
eleventh vertebra there is a distinct exogenous process, standing out 
twenty or twenty-five millimeters from the surface of the centrum to 
the end of which is attached the rib. This process is equally as 
prominent, or more prominent on the next two centra, the twelfth 
and thirteenth. The rib of the twelfth vertebra is intermediate in 


Apr. 1903. Norra AmMERIcAN PLEsIosaurs—WILLISTON. 63 


length between that of the eleventh and of the thirteenth. On the 


‘last cervical centrum, the thirteenth, the twelfth rib is long, heavy 


and stout, more than half the length of the first dorsal. It is nearly 


as stout as any of the following, but tapers somewhat distally, though 
“ ending in a truncated, cartilaginous extremity. The distal end of the 


eleventh rib is lost. The first dorsal rib resembles the one preceding 
it, though longer. The second dorsal rib has acquired nearly the full 


_ length of the thoracic series. In the ninth rib there is a beginning of 


a diminution in size; the rib is less thick, a little shorter, and less 
expanded at its extremity. The twelfth rib is completely preserved; 
it is yet smaller and thinner than the eleventh, though still possessing 
a cartilaginous extremity. Of the following ribs, only the heads of 
some are preserved. ; 


DiapopHyses.— The diapophyses occupy an unusually low position _ 
on the arch of the whole dorsal series, as do also the cervical ribs. 
They have not been wholly freed from the matrix, and their relation 
to the articular process is determinable only in slight part in a few of 
the posterior vertebrae. The arch, like the cervical ribs, is united by 
a strong, persistent suture, evidently an adult character, since the 
sutures of the atlanto-axial complex have been entirely obliterated. 
The process of the first dorsal is short, compressed, and somewhat 
expanded at each extremity; it clearly springs from below the dorsal 
surface of the centrum. As already described, the last cervical rib, 
but little shorter than the first dorsal rib, is attached to a short 
process which arises, apparently wholly, from the centrum. The 
diapophysis of the first dorsal is less than twice the length of this 
process, and so much like it that its sutural connection with the 
centrum is the chief distinctive difference. The second dorsal dia- 
pophysis is a little stouter than, and about twice as long as the first. 
Its articular surface for the rib is larger, flattened, and looks down- 
ward and outward. The fourth and fifth processes have attained the 
maximum size of the series. They have a narrow, concave ventral 
border, more strongly concave posterior border, a flattened, expanded 
proximal end for union with the centrum and an expanded distal 
extremity with its flattened oblique costal surface. The height of the 
process distally, and its expansion beyond the plane of the articular 
zygapophyses, can not be determined. It is very evident, however, 
that the diapophyses lie below the plane of the zygapophyses, in 
which they differ markedly from the diapophyses of Do/ichorhyn- 
chops, where, throughout most of the dorsal vertebra, they are placed 
wholly above the plane of the zygapophyses. The succeeding dia- 


64 Fietp CotumpiaN: MusEuM—GEo_ocy, VoL. II. 


pophyses, to the sixteenth dorsal, scarcely differ in their shape and 
relations to the centrum. These vertebre may, therefore, be properly 
called thoracic. From the seventeenth vertebra to the last one 
preserved, the twenty-second post-cervical, the diapophyses decrease 
rapidly in size, the last being scarcely more than half the length of 
the fourth or fifth. In these posterior processes the proximal articu- 
lation of the arch is as broad as in any of the others, but the distal 
end of the process is more compressed, with only a small surface for 
the small presacral ribs... Over the twentieth vertebra the matrix has 
been cleared away sufficiently to disclose a posterior zygapophysis. 
The free diapophysis in this vertebra is about fifty millimeters in 
length, thirty in height, and about twenty in width. The posterior 
zygapophysis arches upward and backward from the base of the free 
process. ; 


MEASUREMENTS. 

| Length of Centrum. | Width of Centrum.| Length of Rib. 
Atlanto-axis, . ; Scag go mm. 
Third cervical, : A ‘ 46 
Fourth cervical, . ‘ K 46 82 mm. . 60 mm. 
Fifth cervical, b 44 - 
Sixth cervical,- ; : : 45 
Seventh cervical, . Wao ci cae ] 
Eighth cervical, . : ; 50 84 74 
Ninth cervical, . : : 50 : 
‘Tenth cervical, . : ; 50 
Eleventh cervical, : ; 53 o4 
Twelfth cervical, . : : 58 
Thirteenth cervical, : 4) 60 220 
First dorsal, . : : ‘ 64 85 260 
Second dorsal, ‘ ; : 68 zi 370 
Third dorsal, : : 73 400 
Fourth dorsal, g . Bf 74 490 
Fifth dorsal, . ; ; : 77 445 
Seventh dorsal, . ! : 77 82 370 
Twelfth dorsal, . : : 77 82 370 
Twenty-second, . : $ 74 82 


LENGTH OF DIAPOPHYSES. 


First, ‘ . 47mm. Fourth, . . 99 mm. Eighteenth, . 75 mm. 
Second, . eh ai Fifth, f WaQg <a Twentieth, yee. See 
Third, . aaa eee Thirteenth, . go “ Twenty-second, 60 “ 


ieee 


esl ~~ 


‘ 


-  Apr.1903. NortTH AMERICAN PLESIOSAURS—WILLISTON. 65 


Among the characters which have been given in the foregoing 
descriptions there are some of more than usual importance, of more 
than generic value. It is quite evident that the form can not be 
placed in the same family with Dolichorhynchops or Cimoliasaurus 
snowti. Just what family this may be I can not say at present. It is 
very evident that we have to do in the plesiosaurs with several dis- 
tinct families, but the material is hardly sufficient yet to clearly define 
them. Several names have already been proposed, based upon partial 
characters, but there is no unanimity in their acceptance, nor can 
there be until much more is known about these animals than is the 
case at the present time. - 

The essential characters of the present genus, so far as known, 
may be summarized as follows: Head large and broad; palatine 
bones broadly contiguous; a strong pterygoid ridge on either side; a 


deep interpterygoid fossa; neck very short; cervical ribs single- 


headed; cervical ribs and vertebral arches united by persistent 
suture; no infracentral vascular foramina. 

Many of these characters, possibly the union of the palatines in 
the median line, are those of Plosaurus; but Pliosaurus has the 
anterior cervical ribs double-headed, a character supposed to be of 
at least family, possibly subordinal value. Of this, however, I am 
very skeptical, and it is possible that a final classification may locate 
this genus with the Pliosauride. 

It is very evident that the elongation of the neck is a specialized 
character in the plesiosaurs, since we can not conceive of any animal 
with so many vertebre in the cervical region from which these animals 


- could be derived. Considering this character alone, /asmosaurus 


would be the most specialized of all the plesiosaurs, and Arachau- 
chenius the most generalized. It isa question, however, whether such 
forms as the present have preserved this primitive character from 


their terrestrial ancestors, with only a slight increase in the number of 


the cervical vertebra, or whether there has been a secondary reduc- 
tion in the number from some long-necked ancestor. That the long- 
necked plesiosaurs are not all specialized throughout, is very evident. 
In the species of Plesiosaurus, a genus of long-necked forms, the 
epipodial bones are far more generalized in character than are these 
bones in the short-necked /o/ycoty/us, where the epipodials have 
become not only broader than long, but have actually increased in 
number to four. That an increase of the number in the cervical 
vertebre is a specialized character has already been affirmed by Baur, 
Dollo and Fiirbringer in the Dolichosaurs. 

It seems also evident that monocranial ribs are a specialization, 


66 Fietp CoLumMBiAN MusEuM—GEOLOoGy, VoL. II. 


not only in these, but in other aquatic air-breathing vertebrates, such — 
as the cetacea, some ichthyosaurs and the mosasaurs, due to environ- — 
mental causes. It is true that all the Squamata show the same single- 
headedness of the ribs, brought about by similar conditions—the lack 
of the necessity of support of the abdominal organs by the ribs in 
animals resting prone upon the ground, or in a medium of nearly the 
same specific gravity as the creatures themselves. 

It is a singular fact that, in many plesiosaurs, vestiges of dicran- 
ial ribs have been retained in the neck, though such have disappeared 
elsewhere in the vertebral column; and this character has been 
retained in both the long-necked and the short-necked types, such as 
Plesiosaurus and Pliosaurus, though utterly wanting in others, suchas 
Elasmosaurus with seventy-two cervicals and the present with only 
thirteen. Did the long-necked forms become differentiated before 
the dicranial character was lost, and have they continued as a distinct 
phyllum until the character was wholly lost? If so, the short-necked 
Pliosaurs must represent a distinct branch of the order which has also 
undergone the same change. 

The Cretaceous plesiosaurs of America, so far as known, are all 
cercidopleural, while many of the European Jurassic forms are | 
‘dicranopleural. 

This is the fourth species of plesiosaur that I know from the 
Fort Benton deposits of Kansas; there are none certainly referred to 
this epoch from other regions, though Arimosaurus grandis Leidy is 
probably of this horizon. The only one of these hitherto described 
is Zrinacromerum bentonianum Cragin, a long-headed form with long — 
mandibular symphysis and short neck, a form indeed approaching, 
possibly identical with Dodichorhynchops. Another form known of — 
which a considerable part of the vertebral column is preserved at the 
museum of the University of Kansas, is of great size, the dorsal centra 
measuring five inches or more in diameter, with a very long neck and 
small anterior cervicals. The specimen is from near Beloit. It 
represents a distinct species that may provisionally be referred to 
Cimoliasaurus or Brimosaurus. A third form is much smaller, about 
the size of Dolichorhynchops osborni, with short neck. The episternum 
is shown in Fig. g and the cervical vertebrae and humerus in Ph 
XXVIII. I suspect that it belongs in 77/nacromerum, though smaller 
than the type species. I have called it provisionally Zrinacromerum 
anonymum 0X. sp. From all these forms the one described may be 
at once satisfactorily distinguished by the entire absence .of infra- 
central vascular foramina. 


_ Apr.1g03. NortH AMERICAN PLESIOSAURS—WILLISTON. 67 


That the species described in the foregoing pages belongs in 
some genus named but not recognizably described from a later epogh 
is not probable, though possible. I have therefore given the genus 
the name Brachauchenius. 


POLYCOTYLUS LATIPINNIS. 


Pappte.—Some years ago an excellent specimen of a paddle of a 
plesiosaur belonging in all probability to Polycoty/us latipinnis Cope, 
was collected by Mr. George R. Allman of Wallace, Kansas, from the 
upper Niobrara chalk of the Smoky Hill river, east of Fort Wallace. 
The bones of the paddle were, for the most part, found in their 
natural relations, but were separated in the collection of them. . The 
radius and ulna of a second paddle, together with some of the smaller 
bones showed weathering, and doubtless had been picked up from the 
surface. It has required but little trouble to fit into their natural 
relations all the bones except most of the phalanges, which, present- 
ing no lateral surfaces for articulation, could only be located from 
their other characters. A careful study of these, however, makes it 
probable that the positions assigned to them in the photograph are 
for the most part correct. Because of the considerable expansion 
distally of the long bone, the paddle is supposed to be the front one, 
but it is quite possible it may be a hind one. Pl. XXI. 

The head of the Awmerus is large and broad, of a flattened ellip- 
soidal form, with the surface nearly evenly convex; it is slightly 
crushed dorso-ventrally. The tuberosity, placed at a slight distance 
beyond the plane of the proximal extremity, is massive. It has two, 
large, flattened, narrowly separated surfaces for muscular attachment, 
placed nearly at right angle to the longitudinal plane of the bone 
and separated from the head by a slight groove on either side, that of 
the ulnar side being the more pronounced. On the ulnar side of the 
tuberosity there is a slight rugosity, as though for muscular attach- 
_ ment: The shaft is narrowest near the upper third of the bone, 
_ where a cross-section would be nearly circular, or slightly greater in 
_ its dorso-ventral diameter. The anterior or radial border is gently 
_ convex on its upper two-thirds, gently concave below to the rectan- 
- gular angle. The posterior border is more deeply concave through- 
out. The distal border has a deep, cupped, thickened facet at right 


68 FieLp CoLuMBIAN MusgEuM—GEOoLocy, VoL. II. 


angles to the dorso-ventral plane, for the radius; a second shorter 
and less thick one for the ulna joins this at a small angle; beyond 
this, the thinned ulnar expansion is lost in the specimen, but doubt- 
less had two facets for the third and fourth bones of the epipodial 
row. On the ventral surface of the bone above, proximad to the 
middle, there is a large, stout rugosity for muscular attachment. The 
very strong muscle attached to it doubtless arose from the ventral 
surface of ‘the coracoid. On the ulnar border of the bone, at its 
middle, there is a more pronounced, ‘though smaller rugosity, for 
. muscular attachment. The peculiar tooth-like projections on the 
outer posterior angle of the coracoid described in Dolichorhyncheps 
osborni probably indicates the origin of the muscle inserted into 
this. rugosity. It may be called the ulnar rugosity. On the 
radial border, a little beyond its middle, there is a smaller and less 
strong rugosity which may be called the radial. The origin of the 
muscle inserted here probably was on the lower part of the scapula. 
The dorsal surface of the shaft is smooth, without muscular roughen- 
ing beyond the tuberosity. The distal portion of the bone is much 
expanded, thickest toward the radial side, and moderately thinned at 
the distal outer margin. 

Of the four muscular rugosities, which doubtless furnished 
attachment for nearly all of the muscles controlling the arm, those of 
the tuberosity are of course the largest, though the large roughening © 
on the ventral side may have been for the insertion of more powerful 
muscles, which were of course much more effective from the greater 
mechanical advantage under which they acted. The movement here, 
though strong, could not have been through a great range. The 
smallest of all, and placed much further away from the fulcrum is 
the radial. The great convexity of the head indicates considerable 
freedom of rotation. The glenoid surface in the articulated skeleton | 
of Dolichorhynchops looks nearly directly outward. The obliquity at 
which the head of the humerus is placed as regards the horizontal 
plane, indicates that the natural resting position of the flipper was at 
about forty-five degrees downward, but I doubt whether the extrem- 
ities of the paddles could have been raised much, if any, above a 
horizontal position. It is further certain that the flippers could not 
have been brought back against the side of the body. The posterior 
angle of the coracoid, projecting as it does beyond the plane of the 
glenoid surface, certainly prevented any great backward movement 


of the humerus. It seems also evident from this position of the cor- — 


acoid, that the paddle was not so pedunculated as restorations usually — 
have them, but that the humerus was largely or entirely hidden in 


= 


Apr. 1903... NortH AMERICAN PLESIOSAURS—WILLISTON. _ 69 


folds of the skin, as was,evidently also the case, not only in the ich- 
thyosaurs, but also in the mosasaurs. 

The largest bone beyond the humerus is the radius. It is 
irregularly four-sided in shape; the longest and convex proximal sur- 
face fits into the radial facet of the humerus; the shortest and non- 
articular border, that adjoining the ulna, is emarginated like its 
opposing border to form with it a small foramen. Doubtless these 
two emarginations represent the last vestige of the terrestrial type of 
the epipodial bones. The outer border of the radius, the second in 
length, is non-articular and thinned, and has an acute angle proxi- 
mally. The outer distal margin is thick for articulation with the 
radiale of the carpus. The inner distal border, next to the shortest 
of the four, is for articulation with the mediale. 

The «dna is next in size to the radius, and is irregularly six-sided. 
The largest, proximal border, is convex, like that of the radius, and 
joins the smaller facet of the humerus. The distal border has three 
facets of nearly equal length, and joining each other in nearly equal 
angles. These facets are for the mediale externally, the ulnare in the 
middle, and for the ulnar supernumerary, internally. On the inner 
side there is a longer but thinner border for articulation with the first 
epipodial supernumerary, while the outer border is emarginated like 
the opposing border of the radius. 

The next bone of this row, articulating with the humerus, and of 
considerable size, is one of doubtful homology. I will call it the first 
epipodial supernumerary. If one follows Marsh in his views of these 
corresponding bones in Bafptanodon, then this bone is the ulna, and 
the one here called the ulna is the medial carpal. But this inter- 
pretation is very doubtful. Zittel thinks this bone in the ichthyosaurs 
is the pisiform, while Woodward calls it the sesamoid; but I doubt 
these interpretations as well. Among the cetacea, the mosasaurs, 
ichthyosaurs and plesiosaurs there is a reduplication of bones, which 
have been variously explained as a splitting of the phalanges, either 
directly or through the intervention of the epiphyses. The latter 
view is hardly possible, since there are no epiphysial ossifications in 
most if not all these reptiles, and besides, there would not be enough 
epiphyses on the normal digit to furnish the great number of phalanges 
seen in some of the forms. The extra digits in some ichthyosaurs 
are also explained by the longitudinal division of the normal phalanges; 
but I cannot believe that this is the correct explanation. I believe 
that the supernumerary digits, phalanges, epipodial or mesopodial 
bones found in such species as this, as well as in most other American 
plesiosaurs, represent entirely new ossifications in cartilaginous 


70 Fietp CoL_umpian Mustum—Geovoey, Vo. II. 


masses, which originally formed the borders or terminations of the 
adjacent bones. These, in the case of the phalanges, have become 
separated to increase the mobility of the fingers, have increased in 
size and ossified, and have in turn given rise to new cartilaginous 
extremities, that have separated and become ossified; that is, the 
growth of the additional phalanges and carpals, as well as the two 
additional bones of the fore arm, was peripheral. The additional 
fingers of the ichthyosaur may be also explained in a similar way. 
The margin of the flipper has become hardened by fibro-cartilage, 
which by the movement of the fingers was broken into segments, each 
of which finally took on ossification. A division of the phalanges by 


segmentation would certainly have to take place immediately in order * 


to preserve the integrity of the paddle as an organ of propulsion. If 
this explanation be correct, then these additional ossifications in the 


fore arm in the present form, as well as in the carpus, are no dis- - 


placed elements, but new ones, without homologies. 

To return to the description from this digression, the fs 
epipodial supernumerary is irregularly five-sided in shape, for articula- 
tion with the carpal, ulna, humerus and second epipodial supernu- 
merary, the longest, inner border, being thinned and non-articular. The 
second epipodial supernumerary is smaller than the first, and is some- 
what elongate, articulating distally with the first supernumerary, 
proximally with the humerus, and with its longest, somewhat convex 
and thinned internal border non-articulate. 

There are four bones in the first row of the carpus, and the same 
number in the second, the inner one of which partakes so strongly of 
-the nature of a phalange that it doubtfully can be called a carpal. 
The first, or radia/e, is a thick massive bone, nearly regularly 
parallelogrammatic in shape, and articulates with four bones. The 
broad proximal end articulates with the radius; the distal surface with 
the first distal carpal; nearly the whole length of the inner side joins 
the medial carpal, leaving a small space at the distal angle for union 
with the second distal carpal; the outer border is rounded and non- 
articulate. The second distal carpal is wanting in this specimen, and 
has been restored. It must, however, have articulated with the 
radiale and mediale proximally, the first distal carpal externally, 
the third distal carpal internally, and the second and third metacarpals. 
A good figure of this bone of the plesiosaur paddle will be found in 
Leidy, Cretaceous Reptiles, plate iv, ff. 13 and 14. The third distal 
carpal begins to assume something of the nature of a metacarpal, 
though a true carpal; it articulates proximally by two unequal facets 
with the ulnare and medial carpals; externally with the second distal 


= wis ee ee pe a D rae 
_— ee ee ee ee eee ee | oe ee oe 


etic 


pli alld ne areal 


* ate sa 


_ Apr. 1903. NortH AMERICAN PLESIOSAURS—WILLISTON. 71 


carpal; distally with the fourth metacarpal, and internally with the 
fourth distal carpal by two facets, leaving an emargination between 
them, which, with the opposing surface, formsaforamen. The fourth 
bone of this row is, I believe, in reality the fifth metacarpal, which 
has receded proximally to articulate with-the first row; with this inter- 
pretation there may have been some displacement of the carpals 
proximally. The bone is elongate, phalange-shaped, articulating 
proximally with the ulnare, externally by two facets, having an 
emargination between them, with the third distal carpal. Distally it 
articulates with a phalange, and on the outer angle with the fourth 
metacarpal. 

The metacarpals are shorter than the first phalanges of their 
respective fingers. The first is nearly square, articulating with the 
first distal carpal, the second metacarpal and its phalange; the outer 
border is similar to that of the first distal carpal. The second meta- 
carpal is a peculiar bone, easily recognizable in isolated examples; it 

_ joins the first metacarpal externally, the phalange distally, the third 
metacarpal internally by articular surfaces, emarginated between 
them, and proximally by two unequal facets, the first and second 
distal carpals. The third metacarpal is also closely wedged in 
between the second and third metacarpals, the phalange and second 
distal carpal. The fourth metacarpal is scarcely distinguishable from 
a phalange; while the fifth of the row seems to be a phalange. 

Of the phalanges only those of the first and fifth fingers are cer- 
tainly placed in the figured paddle; the others must have been, in 
the living animal, very nearly as they are here figured, but the 
absence of distinct lateral articular facets renders the assumed loca- 
tions uncertain. The proximal ends of the outer four of the first row 
are in nearly the same straight line, but those of the inner. fingers 
become successively less and less elongate, giving an increased 
‘obliquity of the articulations, and more and more definite interlock- 
ing of the bones. Those of the first and fifth digits are more or less 
thinned on the free borders, while those of the intervening fingers 
have the sides more or less flattened, with a greater thickness dorso- 
ventrally than from side to side. The distal bones, however, become 
more and more flattened from above. They are all gently hour-glass 
shaped. There are at least ten phalanges in the first finger, fifteen 
in the second, and perhaps as many as twenty in some of the others. 


72 Fietp CoLumpian MusrtumM—GEo .ocy, VoL. II. 


-  POLYCOTYLUS ISCHIADICUS, N. sP. 


I give this name provisionally to a species from the Niobrara 
Cretaceous of western Kansas, represented by a number of bones in 
the University of Kansas Museum, the most characteristic of which 
are shown in Pls. X and XXVI. There is no assurance what- 
ever, however, that they belong in this genus; on the other hand they 
may belong with the type species, ?. /atipinnis, or they may belong 
to some unrecognized genus. The ischia, it is seen, differ very 
markedly from the corresponding bones of Dodlichorhynchops osborniin 


the shorter length of the symphysial portion, in the greater breadth of, 


the neck, and in the smaller extent of the cartilaginous rim posteri- 
-orly. The bones are also more massive and the face for the ilium is 
larger. The ilia also are materially different, in the greater expan- 
sion proximally, and in the absence of the lateral angular face dis- 
tally. They have a somewhat curved neck, with a rounded head 
showing a cartilaginous surface. The transverse processes of the 
sacral vertebra are more massive than in that species, with a consid- 
erable expansion proximally, a cylindrical shaft and a terminal, some- 
what oblique face for articulation with the ilium. The somewhat 
compressed sacral vertebra is shown from its ventral surface. 
A specimen from the Niobrara in the Kansas Museum, comprising 
a number of caudal vertebre and a portion of the pelvis, I refer with 
much more assurance to P. /atipinnis Cope. The vertebre differ very 
materially from the present, and the probability is, therefore, that /. 
ischiadicus is not a synonym of P. latipinants. 


PLESIOSAURUS GOULDII. 


Plesiosaurus gouldii Williston, Kansas Univ. Quart. vi, p. 57, Jan. 1897- 


Among the material collected in the Lower Cretaceous shales of 
Clark county, Kansas, by Prof. C. N. Gould, and now preserved in 
the museum of the University of Kansas, are the remains of at least 
three different forms of Plesiosaurs, all, however, represented by 
rather incomplete material. | Portions of one of these forms (P/eséo- 
saurus mudgei (?) Cr.) are figured elsewhere in this paper; another 


Apr. 1903. NorrH AMERICAN PLESIOSAURS—WILLISTON. 73 


was briefly described by me several years ago under the name of 
Plesiosaurus gouldit. The species is referred to Plesiosaurus because 
no better place is known for it; in all probability it really belongs to 
some other genus. The species was based upon several dorsal ver- 
tebre in fairly good preservation, one of which, the best, is herewith 
figured. (Pl. XXVII.) 

The specimen shows little compression, and its form is doubt- 
less normal. The anterior face is rather deeply ‘concave, cordate in 
outline, with a small neural depression above. The anterior zyga- 
pophyses are spout-like, the notch between them not extending 
further than the middle of the articular surfaces. The spine is 
rather short and small. The transverse processes are compressed, 
springing in part below the neural canal from the base of the arch. 
The body is compressed in the middle, forming an obtusely rounded 
surface below. About midway on the sides, below the lower root of 
the transverse processes, the side is pinched in, with a small vascular 
foramen at the bottom of the depression. ; 

The vertebra described probably belongs near the sacrum. Its 
measurements are as follows: 


Width of anterior end of centrum : : : eve 1tO%Mmm: 
Vertical diameter, same end : : } 3 : Pee 15 
Length of centrum Aa eae RE ‘ <i AQ 
Height of vertebra A . ; : A : ‘ ASE? ) 
Expanse of transverse processes ; : F ; See 
Width of neural canal ; : z : ; : nia 
Expanse of anterior zygapophyses : : : ‘ oor ee 


PROPODIAL BONES OF YOUNG PLESIOSAURS. 


It is an interesting fact that isolated propodial bones of young 
plesiosaurs are not at all rare in the Kansas chalk ; no more so indeed 
than are bones of the adult animals. I have seen more than a score 
of such, and four or five are now preserved in the museum of the 
University of Kansas; there are many others in the Yale museum. 
Four of these bones are shown in Pl. XXIII; a fifth one, more immature 
than any of those, is figured in Pl. XXII, Figs. 1-4. All such 
bones are composed of more dense tissue than is observed in adult 
bones. Especially is the structure dense in the youngest specimen 
here figured. In this specimen the head of the bone is not at all dif-. 


74 ~ Fretp Cotumpian MuseumM—Geo toey, VoL. II. 


ferentiated, nor are there any muscular markings. On the posterior 
border, near where the ulnar rugosity should be, there are the open- 
ings of two large canals, one on either side of the margin (é and ¢ of 
the figures). On what seems to be the ventral surface, near the 
front border of the bone and nearly opposite the other openings, 
there is a large one with its mouth, as in the others, directed distally. 
On the dorsal surface, and near the middle transversely, there is a 
fourth opening, much smaller than the others. All of these canals | 
unite near the center of the bone in a rounded cavity or ampulla, as 
shown in Figs. 3 and 4. In Pl. XXIII, Fig. 1, a large opening is seen 
on the posterior border below a rugose space, and another opening 
is seen towards the front leading into a groove. This was apparently 
a canal leading into a groove on the opposite side of the bone in the 
uninjured specimen, with another opening corresponding to the fora- 
men which lead into a groove shown in the photograph on the 
exposed surface of the bone. The bone was, however, injured before 
I studied .it, as is indicated by the restored border in the figure. 
The posterior opening probably corresponds to the united 4 and ¢ of 
the other figures. In Fig. 2 of this plate is also seen a foramen on 
the posterior margin of the bone (the left one of the figure). All 
these three bones are probably humeri. Figs. 4 and 5 of the plate do 
not show these canals; from their shape they are probably femora. 
In Fig. 1, Pl. XXII, there is seen at the lower margin a groove 
(e), partly converted into a canal, which probably corresponds to one 
or the other of the grooves of Fig. 1, Pl. XXIII. I believe this 
groove corresponds to, the ectepicondylar groove or foramen of the 
chelonia, lacertilia, Belodon, Champsosaurus, and some of the notho- 
saurs and ichthyosaurs. I may add that a similar groove is sometimes 
indicated in the humerus of the mosasaurs, as shown in Pl. XLIV, 
Vol. IV of the University Geological Survey of Kansas. Why these 
canals and grooves should disappear in the adult humerus is not 
apparent; they are doubtless for the passage of vessels. The 
ampulla at the junction of the four canals in the embryonic bone is 
between the apices of two conical ‘‘epiphyses,”’ the larger epiphysis 
occupying the chief part of the distal portion of the bone, the smaller 
one the proximal. The fractured specimen discloses these epiphyses 
with a smooth rounded surface, as shown in Pl. XXII, Fig. 3, 
the outer part peeling away as does the bark from a tree. 

This ephiphysial-like method of ossification has been compared 
with a somewhat similar structure in the Chelonians as an evidence of 
relationship between the two orders of reptiles. 


Apr. 1903. NORTH AMERICAN PLESIOSAURS—WILLISTON. 75 


A PECULIAR FOOD HABIT OF.THE PLESIOSAURS. 


More than twenty years ago, Professor B. F. Mudge published, 
in the First Biennial Report of the Kansas State Board of Agricul- 
ture (p. 62), the following: ‘‘In the Plesiosaurs we found another 
interesting feature showing an aid to digestion, similar to that of many 
living reptiles and some birds. This consisted of well-worn siliceous 
pebbles, from one-fourth to one-half an inch indiameter. They were 
the more curious, as we never found such pebbles in the chalk or 
shales of the Niobrara.’”’ The specimens which led to this conclusion 
were collected while I was a member of Professor Mudge’s party, and 
are now preserved in the Yale collection. Nearly ten years ago some 
plesiosaur bones collected near Ellsworth, Kansas, from the Benton 
limestone, were sent to the Kansas University museum, together with 
a lot of siliceous stones, with a request for information concerning 
both. At the first opportunity I visited the locality whence they had 
been discovered and collected what had been left of the specimen. 
The bones were in a poor state of preservation, due to the effects of 
frost, but by carefully digging over the shale in which they occurred 
we obtained about one hundred and twenty-five of the pebbles, 
together with several dorsal vertebrae and ribs. Some of the pebbles 
were still attached to the ribs by the original matrix, making it cer- 
tain that their deposition was contemporaneous with that of the skel- 
eton. The plesiosaur is one of the largest of the order, the dorsal 
centra measuring five or more inches in diameter. In all probability 
the species is identical with that mentioned in the preceding pages 
as coming from the vicinity of Beloit. It is impossible to 
determine the genus, and the species is yet undescribed. The 
pebbles vary in weight from less than one gramme to more 
than one hundred and seventy grammes. The smaller ones were 
worn into more or less perfect ellipsoids, but the larger ones are 
more irregular in shape, having suffered less abrasion. It seems 
probable that the most of the pebbles had been obtained by the 
animal from the sea beaches bordering the Black Hills, but nota 
few of them, consisting of red quartzite, are quite identical with the 
quartzite boulders so often found in the drift of eastern Kansas, 
which have come from the vicinity of Sioux City, Iowa. 

The specimens show conclusively that the pyloric orifice of the 
plesiosaurs must have been well provided with a sphincter, and that 
no solid substances passed into the intestinal canal. One need 


76 Fietp CoLtumpian MusrtumM—Geotocy, Vot. II. 


never expect to find plesiosaur coprolites containing undigested 
remains of bones or other solid material. 

The nearest place where the animal could have found such 
pebbles on the sea beaches must have been several hundred miles 
away from Ellsworth, where the animal finally perished. We may 

conclude, hence, that the plesiosaurs were roving animals. 

Since the discovery of this specimen two others with siliceous 
pebbles have been received at the Kansas University museum, one 
from the Niobrara of. Kansas and the other from the Comanche Cre- 
taceous of Clark County, Kansas (Pl. XXIX.) In neither of these 
cases were the pebbles worn into such regular figures as in the 
Benton specimen, and all the pebbles were dark in color, none of 
them quartzite. 

What the use of these pebbles was I will not venture to Say. 
They may have served as a sort of weight to regulate the specific 
gravity of the animals, or they may have been swallowed accidentally. 
If, as I believe probable, the plesiosaurs were in the habit of feeding 
upon invertebrate animals, seeking such in the shallow muddy 
bottoms, the pebbles may have been taken with their food uninten- 
tionally. I doubt this, however. I may add that all specimens do’ 
not reveal similar pebbles. In the specimen of Dodichorhynchops 
osborni, described in the preceding pages, where one would certainly 
expect to find them, there were none. Possibly it was only the 
broad-headed and more omnivorous kinds that resorted to this 
peculiar diet, the long-snouted types pene more exclusively fish-eat- 
ing in habit. 

Crocodiles and seals are said.to have similar habits, but I have 
not learned the reason therefor. 

Many years ago, a similar habit was recorded of the teleosaurs 
by Geoffroy St. Hilaire, in the Memoires de l’Acad. des Sci., xxii, p. 
48, 1833. Of the plesiosaurs, the only recorded notice, other than by 
myself, that I can find of such habits is the following by Seeley 
(Quart. Jour. Geol. Soc., xxxiiil, 1877, p. 546): 

‘‘In the lower dorsal region of the animal (M/uraenosaurus gard- 
ner?) about a peck of ovate and rounded pebbles occurred, varying in 
size from a diameter of a quarter of an inch to a length of nearly two 
inches. They are chiefly of opaque milky quartz, several are of 
black, metamorphosed slate, and a few of altered, fine-grained sand- 
stone and ironstone, some of the pebbles showing a veined character, 
such as might be derived from the neighboring Paleozoic rocks of the 
north of France. Pebbles being of such rare occurrence in the Gault, 
it would seem natural to account for these associated ones by the 


> 


Apr. 1903. Nortu AMERICAN PLESIOSAURS—WILLISTON. 77 


hypothesis that they were swallowed by the animal with food, as is 
the case with several living reptiles and birds. If this view should be 
held admissible, it would suggest that, as the teeth were too small. 
for anything but prehension, a structure analogous to a gizzard or the 
stomach of an edentate, may have used these pebbles to assist in 
breaking up or crushing the food on which the saurian lived.” 


. 


core 

Ht 
Bath 
ey ata 


é Y 
AA cat 

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Fg a 


MG: 1G NOISES 


SHOHD 


‘HEROES 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. |. 


es 


*~ wv v8 ‘au 


SKELETON OF DOLICHORHYNCHOPS OSBORNI, 


vee!) Se ei ant og 4 i 


PENX 


3 to Inde 


6EOI.OGY, Ps 


10 namiseqe sqy 


¢ 


, BAY Paawrwe, ofK Ski. OF 


Renan) a 


PY Skull of type specimen of 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. Il. 


~~ re 


ENT De eee ae 


} 


SIDNEY PRENTICE, DEL. SKULL OF DOLICHORHYNCHOPS OSBORNI. 


i 


Ver 


e 


Ln 


4 


BES Tee eee Grote Pt. st. 


Fs Se 


ee 


PiaTe Ill. 


Skull of Dolichorhynchops osborni. X7/24. 

Fig. 1, type specimen, from the right. 

Fig. 2, restoration, from the left. 

ang, angular; d@, dentary; eo, exoccipital; ef, bsletareeosa: JS, frontal; 7, jugal; 
m, maxilla; #, nasal; fa, parietal; Jet, petrosal; A¢, pterygoid; A/, palatine; pm, 
premaxilla; Af, prefrontal; of, postorbital (postfronto-orbital?); g, quadrate; ¢g/, 
quadratojugal; sc, sclerotic plates; so, supraoccipital; sg, squamosal; sr, surangu- 
lar; v, vomer. 


FIELD COLUMBIAN MUSEUM. 


GEOLOGY, PL. Ill. 


SIDNEY PRENTICE, DEL. 


Cures cal 
MRULL UF VVULICNURMTINERUrs USBUKINI, 


; ee pnentipnaistnth nase 5 
ae oa he eae ite | a eke 
a at ; a ae ONS EF. repay te 


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2 


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gy) earning ir ents miata 


ora poll Bee i Set : 
Fes ia rity 


a eo Se Bp 


mn nl lignans 


PiaTe IV. 


Skull of Dolichorhynchops osborni. XK1/3 

Fig. 1, from above. 

Fig. 2, from below. 

bo, occipital condyle; ev, external nares; ef, ectopterygoid; f frontal; zm, 
internal nares (the letters are on the anterior end of the palatine); 7, jugal, mx, 
maxilla; Za, parietal; Af prefrontal; fm, premaxilla; Af, pterygoid; fof, post- 
orbital; g, quadrate; g7, quadratojugal; sg, squamosal 


GEOLOGY, PL. IV. 


FIELD COLUMBIAN MUSEUM. 


SKULL OF DOLICHORHYNCHOPS OSBORNI. 


Pate V. 


Inner side of the left mandible of various reptiles. 

Fig. 1, Sphenodon. 

Fig. 2, Chelydra. 

Fig. 3, Alligator. 

Fig. 4, Varanus. 

Fig. 5, Cimoliasaurus snowt?t. 

art, articular; sur, surangular; amg, angular; c, coronoid; Ja, prearticular; 
sp, splenial; d, dentary; mg, Meckel’s groove. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. V. 


INNER SIDE OF THE LEFT MANDIBLE OF VARIOUS REPTILES. 


FIELD CCLUMOIAN MUSEUM. 


CERVICAL VERTEBRA 


| 


< 
\ 


HieHROHOLS 


Gss 


&S 


ae ioe a 


OLOGY, PL 


Wy 


PiaTe VI. 


Fourth to eighteenth cervical vertebre of Dolichorhynchops osborni, from 
below. X4/I5. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. VI. 


CERVICAL VERTEBRA OF DOLICHORHYNCHOPS OSBORNI. 


ie et 
Vian, 
ray % 
« 


PuaTE Vil. 


Seventh to fourteenth cervical vertebre of Dolichorhynchops osborni, from 
the side. X4/I5. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL, Vil. 


CERVICAL VERTEBRA OF DOLICHORHYNCHOPS OSBORNI. 


FIELD COLUMBAN MUSEUM. GEORGY, Pie VI 


PuaTE Vill. 


Median cervical vertebrz of Dodichorhynchops osborni, from the front. 4/15. 


FIELD COLUMBIAN MUSEUM, GEOLOGY, PL. Vill. 


CErRviCAL VERTEBRA OF DOLICHORHYNCHOPS OSBORNI 


Sagi ea 
at tae ae 
DALY Ser 

a % 


9 ees 
yy 


So arteal 
= oy 4 


PLaTE IX, 


Posterior cervical vertebrz of Dolichorhynchops osborni, from behind. 4/15. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. IX. 


CERVICAL VERTEBRA OF DOLICHORHYNCHOPS OSBORN! 


PLATE X. 


Left series, distal caudal vertebrae of Dolichorhynchops osborni, from above, 
11/24. 

Right series, cervical vertebre of Polycotylus ischiadicus, from below. 
11/24. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL, xX. 


Lert SERIES, CauDAL VERTEBRA OF DOLICHORHYNCHOPS OSBORNI 
RiGHT Series, Cervical VERTEBRA OF POLYCOTYLUS ISCHIADICUS. 


* 


ce 5 


PLATE XI. 


Thoracic and abdominal ribs of Dolichorhynchops osbornt. X1/3. 


FIELD COLUMBIAN MUSEUM. 


CHOPS OSBORNI, 


RiBs OF DOLICHORHYN 


panel 


FIELD COLUMBAN 


MPT EM. 


ete Epoch eee Cae 


PvaTE XIl. 


Bones of pectoral girdle of Dolichorhynchops osborni. X7/13. 
Upper left figure, right scapula, from without. 

Upper right figure, left scapula, from within. 

Lower left figure, left clavicle, from above. 

Lower right figure, episternum, from below. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. Xi 


BONES OF PECTORAL GIRDLE OF DOLICHORHYNCHOPS OSBORNI. 


zi 


. 


ase 
re 


PLaTE XIII. 


Bones of pectoral girdle of Dolichorhynchops osborni, from above. 


Upper left figure, left clavicle. 
Upper middle figure, episternum. 
Upper right figure, scapula. 
Lower left figure, right coracoid. 
Lower right figure, humerus. 


X 3/14. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. XIil, 


PECTORAL GIRDLE OF DOLICHORHYNCHOPS OSBORNI, FROM ABOVE. 


LUE TSS 


PraTe XIV. 


Pectoral girdle of Dolichorhynchops osborni. 

Upper figure, left clavicle, scapula and upper extremity of coracoid, articu- 
lated, from above. X1/3. 

Lower figures, scapulo-clavicular girdle of same, from in front. 1/4. 


FIELD COLUMBIAN MUSEUM, GEOLOGY, PL. 


PECTORAL GIRDLE OF DOLICHORHYNCHOPS OSBORNI. 


LO COLUMBIAN MUSEUM. ; GEOLOGY, PL, x 


ae 


PLATE XV. 


Complete pectoral girdle of Dolichorhynchops osborni, from below, articu- 
lated. 1/4. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. XV. 


PECTORAL GIRDLE OF DOLICHORHYNCHOPS OSBORNI. 


oe 


Ps 
sy 


Pl pe he 


oe 


ne 


estate sate gneae rs 


aes 


Sin Mae gy 
ae ay 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. XVI. 


PUBES OF DOLICHORHYNCHOPS OSBORNI. 


a Xe 4 = ee 7 ie 


oe te See tegen nels 


ih Ee el 


PN! 


CRA YNCHOFS: GSHORN: 


Fiugek 


FIELO COLUMBIAN MUSEUM. 


Pirate XVII. 


Right ischium (left figure) and ilium of Dolichorhynchops osborni, visceral 
surface. X3/8. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. XVII. 


ISCHIUM AND ILIUM OF DOLICHORHYNCHOPS OSBORNI. 


J i he 


- Pactonay ‘ano Pewee Satoies be P 


PLaTE XVIII. 


Outlines of pectoral and pelvic girdles of different plesiosaurs. 

Fig. 1, pectoral girdle of Cryptoclidus oxonitensis, after Andrews. 

Fig. 2, pelvic girdle of same, after Andrews. 

Fig. 3, pelvic girdle of Cimoliasaurus sp, from a photograph furnished by 
Prof. Fraas. 

- Fig. 4, pelvic girdle of Crmoliasaurus trochanterius, after Lydekker. 

Fig. 5, pectoral girdle of Plesiosaurus sp, from photograph from Prof. Fraas, 

Fig. 6, pectoral girdle of /urenosaurus, after Andrews. 

Fig. 7, pelvic girdle of same, after Andrews. 

Fig. 8, pelvic girdle of same, from the side, after Andrews. 

tc, episternum; c/, clavicle; sc, scapula; co, coracoid; fz, pubis; zs, ischium. 


~ 
= 


yO PX. 


: 


siti Pm 


PLaTe XIX. 


Pectoral and pelvic girdles of plesiosaurs. 

Fig. 1, pectoral girdle of Plestosaurus, after Owen. 

Fig. 2, pectoral girdle of Plestosaurus, after Woodward. 

Fig. 3, pectoral girdle of Plestosaurus laticeps, after Owen. 

Fig. 4, pectoral girdle of Zlasmosaurus platyurus, after Cope. 

Fig. 5, pelvic girdle of same, after Cope. 

ze, episternum; c/, clavicle; sc, scapula; co, coracoid; J, pubis; és, ischium. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. XIX, 


i 
. 


eceel+ $c 


py 


TO eww easy 
-<-<---"" 


Te éeae* 


PECTORAL AND PELVIC GIRDLES OF PLESIOSAURS. 


Magis bo ae ta 


“F 


PLATE XX. 


Limbs, as mounted, of Dolichorhynchops osborni, dorsal surface. X1I/4. 
Left figure, right pectoral paddle. 
Right figure, right pelvic paddle. 


FIELD COLUMBIAN MUSEUM GEOLOGY, 


} 
, 
) 


mielg 


Tele \¢ 


mr pele 


1 
ei 
PIUPTE 


Ribs ie \f; 


| 


4 


si 


‘ie 
' Si, 
be 
se 


Rat: 


B/ 
&® 

P 

> 


el I) 


LIMBS OF DOLICHORHYNCHOPS OSBORNI. 


Set COLUMHAR MUSEUM. SEOLOBY, PL, BML. 


ee 


Isiotoeg jilgirl 


i 


} 


a De 


Panos OF Poivcotruus Uererinns, 


PLATE XXI, 


Right pectoral paddle of Polycotylus latipinnis Cope, palmar surface. 1/6. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. XxXI. 


PADDLE OF POLYCOTYLUS LATIPINNIS. 


GEOLOGY, PL. Xr 


o~ 


Paoropisc BON OF Yous PLeecsaur, . RTLANTOLASISUOR (DOUICHORMYN THORS ORECRNE 


PLATE XXII. 


Figs. 1-4, propodial bone of young plesiosaur, from Niobrara Cretaceous. 
X 3/4. 

Fig. 5, atlanto-axis of Dolichorhynchops osborni, from the side. 3/4. 

ati, atlantal intercentrum; ax7, axial intercentrum; , atlantal neurapophysis; 
0, odontoid; 7, pit for reception of axial rib; 2a, axial neurapophysis; 2, zyga- 
pophysis. 


ie 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. XXII. 


PrRopopiaL BONE OF YOUNG PLEISOSAUR. ATLANTO-AXIS OF DOLICHORHYNCHOPS OSBORNI. 


% 


SUNVSOISSI 


a 
¢ 
= 
= 
‘x 
o 
te 
7 
e 
Oo 
$ 
S 
& 


~ 


J2 Sis 


MJ 


‘NASA NVERM 


PLATE XXIill. 


Propodial bones of young plesiosaurs, from the Niobrara Cretaceous of Kan- 
sas. X1/2. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. Xxill. 


PROPODIAL BONES OF YOUNG PLESIOSAURS 


—<<«_—-—— 


a i as 


il Te 


MUSEUM. 


RATE GP 


& 


BATH ACRE 


. 
“a 


PLATERXXIV, 


Palatal view of type specimen of Brachauchenius lucasi (redrawn from 
photograph and sketch). 3/25. 

pi, pterygoid; ef, ectopterygoid; Ja, palatine; fs, parasphenoid; v, vomer; 
és, basisphenoid. 


XXIV. 


PL. 


GEOLOGY, 


FIELD COLUMBIAN MUSEUM. 


PALATE OF BRACHAUCHENIUS LUCASI. 


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FIELD COLUMBIAN MUSEUM, GEOLOGY, PL. XXV. 


VERTEBRA ANDO RiBS OF BRACHAUCHENIUS LUCASI. 


age 


PLATE XXVI. 


Pelvic bones of Polycotylus ischiadicus Willist., visceral surface. 1/3. 
zs, ischium; 27, ilium; sf, sacral rib; sv, sacral vertebra. 


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ae SEGLOGY, Pic REVS 


FIELD COLUMBAN MUSEUM. SEG 


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SasTeanaw Aup Portion ive ska OF PLESIOSAGRUS MUOGEL 


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Fig. 2, rig 3; 
Dorsal Vertesra OF PLESosAURUS GouLoit, 


PLaTE XXVIl. 


Fig. 1, episternum and portion of clavicles of Plesiosaurus mudget ( ?) Cragin, 
from below. X1/2. 

Fig. 2, dorsal vertebra of Plestosaurus gouldii (type specimen), from the 
front. X1/2. 

Fig. 3, the same, from the side. 1/2. 

Drawn by Sidney Prentice. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. XXvVII. 


Fig. 1. 
EPiSTERNUM AND PORTION OF CLAVICLES OF PLESIOSAURUS MUDGEI. 


Fig, 2, Figy:3: 
DorRSAL VERTEBRA OF PLESIOSAURUS GOULDII. 


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CYELD: COLUMBAN MUSEUM. 


TRACHEA eat 


PLATE XXVIII. 


Trinacromerum anonymum Willist. 3/11. 
Upper figures, parts of ilium and coracoid. 
Lower figures, humerus, as restored, and cervical vertebre. 


FIELD COLUMBIAN MUSEUM. GEOLOGY, PL. XXV 


TRINACROMERUM ANONYMUM. 


ler " 
GEDLOGY, PL. KIA 


Stomsnw Pemas’ see 
a * Le. Fe 
‘ 
* 


PLATE XXIX. 


“Stomach pebbles,” vertebrae and femur of Plestosaurus mudgei Cragin, reduced. 


€1ELD COLUMBIAN MUSEUM. GEOLOGY, PL. XXIX, 


“STOMACH PEBBLES” OF PLESIOSAUR. 


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Paha ct 


ae 


UNIVERSITY OF ILLINOIS-URBANA 


3 0112 084203212 


